There are various approaches when trying to extend the Textile markup that RedCloth understands with own tags or syntax. Some approaches documented on the net have changed or don’t work any more, since RedCloth has been rewritten in Version 4.

Below is a fairly robust aproach, that is based on the assumption, that RedCloth leaves HTML tags inside the markup untouched and passes them on to the application consuming the translated markup.

The below code has been used in the Madek project. Madek, a Ruby On Rails application, uses irwi which provides a Wiki to Madek. And finally irwi uses RedCloth to do the rendering from Textile to HTML. That’s where we hook in.

We want to have a few special tags, which make the life of the Madek Wiki admin simpler, by letting him write the following inside the Textile markup:

[media=210      | Das Huhn]
[screenshot=210 | Das Huhn]
[video=210      | Das Huhn]

That will finally produce this HTML output:

<a href="/media_entries/210">Das Huhn</a>
<img src="/media_entries/210/image" title="Das Huhn"/>
<video src="/media_entries/210/image" title="Das Huhn"/>
  <a href='/media_entries/210'>(see video)</a>
</video>

Here’s the implementation:

class RedClothMadek

  ActionView::Base.sanitized_allowed_tags << 'video'

  def initialize
    require 'redcloth'
  end

  def format( text )
    ::RedCloth.new( replace_madek_tags(text) ).to_html
  end

  # Transforms the follwing Textile markups:
  # 
  #   [media=210      | Das Huhn] -> <a href="/media_entries/210">Das Huhn</a>
  #   [screenshot=210 | Das Huhn] -> <img src="/media_entries/210/image" title="Das Huhn"/>
  #   [video=210      | Das Huhn] -> <video src="/media_entries/210/image" title="Das Huhn"/>
  #                                    <a href='/media_entries/210'>(see video)</a>
  #                                  </video>
  #
  def replace_madek_tags( text )

    # unfortunately having multiple matches in gsub doesn't seem to work, therefore
    # we fall back to $1 $2
    #
    text.gsub(/[\s*media\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,txt|

           "<a href='/media_entries/#{$1}'>#{h($2)}</a>"                 }.

         gsub(/[\s*screenshot\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,title|

           "<img src='/media_entries/#{$1}/image' title='#{h($2)}'/>"    }.

         gsub(/[\s*video\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,title|
           "<video src='/media_entries/#{$1}/image' title='#{h($2)}'>" +
             "<a href='/media_entries/#{$1}'>(see Wideo)</a>" +
           "</video>"  }
  end

end

And finally, irwi needs to be told to use that formatter instead of RedCloth directly. From config/environment.rb:

require "#{Rails.root}/lib/red_cloth_madek.rb"
Irwi.config.formatter = RedClothMadek.new

Tomáš Pospíšek

There are various approaches when trying to extend the Textile markup that RedCloth understands with own tags or syntax. Some approaches documented on the net have changed or don’t work any more, since RedCloth has been rewritten in Version 4.

Below is a fairly robust aproach, that is based on the assumption, that RedCloth leaves HTML tags inside the markup untouched and passes them on to the application consuming the translated markup.

The below code has been used in the Madek project. Madek, a Ruby On Rails application, uses irwi which provides a Wiki to Madek. And finally irwi uses RedCloth to do the rendering from Textile to HTML. That’s where we hook in.

We want to have a few special tags, which make the life of the Madek Wiki admin simpler, by letting him write the following inside the Textile markup:

[media=210      | Das Huhn]
[screenshot=210 | Das Huhn]
[video=210      | Das Huhn]

That will finally produce this HTML output:

<a href="/media_entries/210">Das Huhn</a>
<img src="/media_entries/210/image" title="Das Huhn"/>
<video src="/media_entries/210/image" title="Das Huhn"/>
  <a href='/media_entries/210'>(see video)</a>
</video>

Here’s the implementation:

class RedClothMadek

  ActionView::Base.sanitized_allowed_tags << 'video'

  def initialize
    require 'redcloth'
  end

  def format( text )
    ::RedCloth.new( replace_madek_tags(text) ).to_html
  end

  # Transforms the follwing Textile markups:
  # 
  #   [media=210      | Das Huhn] -> <a href="/media_entries/210">Das Huhn</a>
  #   [screenshot=210 | Das Huhn] -> <img src="/media_entries/210/image" title="Das Huhn"/>
  #   [video=210      | Das Huhn] -> <video src="/media_entries/210/image" title="Das Huhn"/>
  #                                    <a href='/media_entries/210'>(see video)</a>
  #                                  </video>
  #
  def replace_madek_tags( text )

    # unfortunately having multiple matches in gsub doesn't seem to work, therefore
    # we fall back to $1 $2
    #
    text.gsub(/[\s*media\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,txt|

           "<a href='/media_entries/#{$1}'>#{h($2)}</a>"                 }.

         gsub(/[\s*screenshot\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,title|

           "<img src='/media_entries/#{$1}/image' title='#{h($2)}'/>"    }.

         gsub(/[\s*video\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,title|
           "<video src='/media_entries/#{$1}/image' title='#{h($2)}'>" +
             "<a href='/media_entries/#{$1}'>(see Wideo)</a>" +
           "</video>"  }
  end

end

And finally, irwi needs to be told to use that formatter instead of RedCloth directly. From config/environment.rb:

require "#{Rails.root}/lib/red_cloth_madek.rb"
Irwi.config.formatter = RedClothMadek.new

Tomáš Pospíšek

There are various approaches when trying to extend the Textile markup that RedCloth understands with own tags or syntax. Some approaches documented on the net have changed or don’t work any more, since RedCloth has been rewritten in Version 4.

Below is a fairly robust aproach, that is based on the assumption, that RedCloth leaves HTML tags inside the markup untouched and passes them on to the application consuming the translated markup.

The below code has been used in the Madek project. Madek, a Ruby On Rails application, uses irwi which provides a Wiki to Madek. And finally irwi uses RedCloth to do the rendering from Textile to HTML. That’s where we hook in.

We want to have a few special tags, which make the life of the Madek Wiki admin simpler, by letting him write the following inside the Textile markup:

[media=210      | Das Huhn]
[screenshot=210 | Das Huhn]
[video=210      | Das Huhn]

That will finally produce this HTML output:

<a href="/media_entries/210">Das Huhn</a>
<img src="/media_entries/210/image" title="Das Huhn"/>
<video src="/media_entries/210/image" title="Das Huhn"/>
  <a href='/media_entries/210'>(see video)</a>
</video>

Here’s the implementation:

class RedClothMadek

  ActionView::Base.sanitized_allowed_tags << 'video'

  def initialize
    require 'redcloth'
  end

  def format( text )
    ::RedCloth.new( replace_madek_tags(text) ).to_html
  end

  # Transforms the follwing Textile markups:
  # 
  #   [media=210      | Das Huhn] -> <a href="/media_entries/210">Das Huhn</a>
  #   [screenshot=210 | Das Huhn] -> <img src="/media_entries/210/image" title="Das Huhn"/>
  #   [video=210      | Das Huhn] -> <video src="/media_entries/210/image" title="Das Huhn"/>
  #                                    <a href='/media_entries/210'>(see video)</a>
  #                                  </video>
  #
  def replace_madek_tags( text )

    # unfortunately having multiple matches in gsub doesn't seem to work, therefore
    # we fall back to $1 $2
    #
    text.gsub(/[\s*media\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,txt|

           "<a href='/media_entries/#{$1}'>#{h($2)}</a>"                 }.

         gsub(/[\s*screenshot\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,title|

           "<img src='/media_entries/#{$1}/image' title='#{h($2)}'/>"    }.

         gsub(/[\s*video\s*=\s*(\d+)\s*\|\s*([^]]+)\s*]/) { |number,title|
           "<video src='/media_entries/#{$1}/image' title='#{h($2)}'>" +
             "<a href='/media_entries/#{$1}'>(see Wideo)</a>" +
           "</video>"  }
  end

end

And finally, irwi needs to be told to use that formatter instead of RedCloth directly. From config/environment.rb:

require "#{Rails.root}/lib/red_cloth_madek.rb"
Irwi.config.formatter = RedClothMadek.new

Tomáš Pospíšek

Problem: I have a web site/page that I visit regularily which I want to annotate with my notes.

More specifically, I was regularly searching through the Homegate real estate hub looking for a new home. It goes without saying that I was again and again forgetting which objects I had already looked at, which objects were really interesting and I should check out more closely.

Therefore the need to annotate search results.

The here presented approach should be applicable for annotation of other web pages as well. It’s based on the observation, that restful web applications need to operate with asset IDs. These asset IDs can be reused to enrich the asset locally with additional data, such as notes. Thus we’re looking for those IDs in specific elements of the page and add a bit of HTML markup to those places.

Of course that aproach only works as long as the web site doesn’t heavily change its markup and doesn’t rendomly change asset IDs.

Here’s a screenshot of regular Homegate search results:

And here’s the same page after scripting it with Greasemonkey:

You’ll notice the input field with the comment in it.

The idea is simple: add an input box to each search result, where you write your comment. When the focus leaves the input box, the comment is stored to localStorage.

Starting with Greasemonkey is quite easy. There are howtos and templates to start from, such as this one.

However, regular JavaScripting and Greasemonkey JavaScripting do not work in exactly the same way:

One of the differences is that Greasemonkey creates a separate JavaScript environment, in which the Greasemonkey scripts are executed. That is calling Javascript contained in the page from Greasemonkey and the inverse calling Greasemonkey scripts from the page is not possible by default. This is on purpose, so that the web page can not detect and not interfere with the Greasemonkey scripts, because you want your Greasemonkey scripts to work allways on some page, whether or not that page likes it or not. Therefore no interference is possible.

Greasemonkey however provides a standard way to access the web page’s scripts, and that’s through the “unsafeWindow” object, which is a reference to the web page’s environment.

I had two mechanisms I had to make accessible using the “unsafeWindow” handle:

• the first was accessing JQuery, which is included by default by the Homegate page. Since I needed to use JQuery functions in my Greasemonkey script, I got a reference to it via the standard Greasemonkey precedure:

    var jQuery = unsafeWindow['jQuery'];

• the second mechanism that needed to cross the boundaries between the web page and Greasemonkey was callbacks from the web page to my Greasemonkey script. This is necessary, because I’m attaching “input” elements to each search result, which contain a note and which, “onblur”, need to call a function that saves the content of the input box. Here’s part that constructs the input element:

    jQuery("<input onclick='event.cancelBubble = true;'" +
                 " onblur='saveComment(this, immoID);'>").insertAfter(immoElement);

And this is the function that gets called back by “onblur”:

    unsafeWindow.saveComment = function(element, immoID) {
      unsafeWindow.localStorage.setItem(immoID, element.value);
    };

The next interesting thing you’ll note is usage of ‘locaStorage’. Support for the latter in browsers does not seem mature yet. One problem I’ve encountered when developing under Firefox 3.6 was that saving to ‘localStorage’ was not possible when cookies were disabled (see this report). Thus you’ll need to permanently enable cookies for Homegate in order for the script to be able to save its data.

Finally, while developing, a major problem was, that Firefox did not show me errors in the Greasemonkey scripts. Thus either the script would work or not work and fail completely silently. That made debugging a bit painful.

So now, here’s the script.

Tomáš Pospíšek

PS: This script also lives at userscripts.org

Problem: I have a web site/page that I visit regularily which I want to annotate with my notes.

More specifically, I was regularly searching through the Homegate real estate hub looking for a new home. It goes without saying that I was again and again forgetting which objects I had already looked at, which objects were really interesting and I should check out more closely.

Therefore the need to annotate search results.

The here presented approach should be applicable for annotation of other web pages as well. It’s based on the observation, that restful web applications need to operate with asset IDs. These asset IDs can be reused to enrich the asset locally with additional data, such as notes. Thus we’re looking for those IDs in specific elements of the page and add a bit of HTML markup to those places.

Of course that aproach only works as long as the web site doesn’t heavily change its markup and doesn’t rendomly change asset IDs.

Here’s a screenshot of regular Homegate search results:

And here’s the same page after scripting it with Greasemonkey:

You’ll notice the input field with the comment in it.

The idea is simple: add an input box to each search result, where you write your comment. When the focus leaves the input box, the comment is stored to localStorage.

Starting with Greasemonkey is quite easy. There are howtos and templates to start from, such as this one.

However, regular JavaScripting and Greasemonkey JavaScripting do not work in exactly the same way:

One of the differences is that Greasemonkey creates a separate JavaScript environment, in which the Greasemonkey scripts are executed. That is calling Javascript contained in the page from Greasemonkey and the inverse calling Greasemonkey scripts from the page is not possible by default. This is on purpose, so that the web page can not detect and not interfere with the Greasemonkey scripts, because you want your Greasemonkey scripts to work allways on some page, whether or not that page likes it or not. Therefore no interference is possible.

Greasemonkey however provides a standard way to access the web page’s scripts, and that’s through the “unsafeWindow” object, which is a reference to the web page’s environment.

I had two mechanisms I had to make accessible using the “unsafeWindow” handle:

• the first was accessing JQuery, which is included by default by the Homegate page. Since I needed to use JQuery functions in my Greasemonkey script, I got a reference to it via the standard Greasemonkey precedure:

    var jQuery = unsafeWindow['jQuery'];

• the second mechanism that needed to cross the boundaries between the web page and Greasemonkey was callbacks from the web page to my Greasemonkey script. This is necessary, because I’m attaching “input” elements to each search result, which contain a note and which, “onblur”, need to call a function that saves the content of the input box. Here’s part that constructs the input element:

    jQuery("<input onclick='event.cancelBubble = true;'" +
                 " onblur='saveComment(this, immoID);'>").insertAfter(immoElement);

And this is the function that gets called back by “onblur”:

    unsafeWindow.saveComment = function(element, immoID) {
      unsafeWindow.localStorage.setItem(immoID, element.value);
    };

The next interesting thing you’ll note is usage of ‘locaStorage’. Support for the latter in browsers does not seem mature yet. One problem I’ve encountered when developing under Firefox 3.6 was that saving to ‘localStorage’ was not possible when cookies were disabled (see this report). Thus you’ll need to permanently enable cookies for Homegate in order for the script to be able to save its data.

Finally, while developing, a major problem was, that Firefox did not show me errors in the Greasemonkey scripts. Thus either the script would work or not work and fail completely silently. That made debugging a bit painful.

So now, here’s the script.

Tomáš Pospíšek

PS: This script also lives at userscripts.org

Problem: I have a web site/page that I visit regularily which I want to annotate with my notes.

More specifically, I was regularly searching through the Homegate real estate hub looking for a new home. It goes without saying that I was again and again forgetting which objects I had already looked at, which objects were really interesting and I should check out more closely.

Therefore the need to annotate search results.

The here presented approach should be applicable for annotation of other web pages as well. It’s based on the observation, that restful web applications need to operate with asset IDs. These asset IDs can be reused to enrich the asset locally with additional data, such as notes. Thus we’re looking for those IDs in specific elements of the page and add a bit of HTML markup to those places.

Of course that aproach only works as long as the web site doesn’t heavily change its markup and doesn’t rendomly change asset IDs.

Here’s a screenshot of regular Homegate search results:

And here’s the same page after scripting it with Greasemonkey:

You’ll notice the input field with the comment in it.

The idea is simple: add an input box to each search result, where you write your comment. When the focus leaves the input box, the comment is stored to localStorage.

Starting with Greasemonkey is quite easy. There are howtos and templates to start from, such as this one.

However, regular JavaScripting and Greasemonkey JavaScripting do not work in exactly the same way:

One of the differences is that Greasemonkey creates a separate JavaScript environment, in which the Greasemonkey scripts are executed. That is calling Javascript contained in the page from Greasemonkey and the inverse calling Greasemonkey scripts from the page is not possible by default. This is on purpose, so that the web page can not detect and not interfere with the Greasemonkey scripts, because you want your Greasemonkey scripts to work allways on some page, whether or not that page likes it or not. Therefore no interference is possible.

Greasemonkey however provides a standard way to access the web page’s scripts, and that’s through the “unsafeWindow” object, which is a reference to the web page’s environment.

I had two mechanisms I had to make accessible using the “unsafeWindow” handle:

• the first was accessing JQuery, which is included by default by the Homegate page. Since I needed to use JQuery functions in my Greasemonkey script, I got a reference to it via the standard Greasemonkey precedure:

    var jQuery = unsafeWindow['jQuery'];

• the second mechanism that needed to cross the boundaries between the web page and Greasemonkey was callbacks from the web page to my Greasemonkey script. This is necessary, because I’m attaching “input” elements to each search result, which contain a note and which, “onblur”, need to call a function that saves the content of the input box. Here’s part that constructs the input element:

    jQuery("<input onclick='event.cancelBubble = true;'" +
                 " onblur='saveComment(this, immoID);'>").insertAfter(immoElement);

And this is the function that gets called back by “onblur”:

    unsafeWindow.saveComment = function(element, immoID) {
      unsafeWindow.localStorage.setItem(immoID, element.value);
    };

The next interesting thing you’ll note is usage of ‘locaStorage’. Support for the latter in browsers does not seem mature yet. One problem I’ve encountered when developing under Firefox 3.6 was that saving to ‘localStorage’ was not possible when cookies were disabled (see this report). Thus you’ll need to permanently enable cookies for Homegate in order for the script to be able to save its data.

Finally, while developing, a major problem was, that Firefox did not show me errors in the Greasemonkey scripts. Thus either the script would work or not work and fail completely silently. That made debugging a bit painful.

So now, here’s the script.

Tomáš Pospíšek

PS: This script also lives at userscripts.org

to visually sort images under Linux doesn’t seem to be a trivial task. I duckduckgo‘ed for a long time and had a look at various image and file managing applications before finding gthumb. And even there, you first need to create a “catalog” and within the catalog a “library” which will finally allow you to manually sort your images. All of which is not documented.

Once you’ve sorted your images, you’d possibly want to export the sorting? Again, no trace of any help or documentation: gthumb catalogs are saved under $HOME/.local/share/gthumb/catalogs/foobar.catalog.

Tomáš Pospíšek

to visually sort images under Linux doesn’t seem to be a trivial task. I duckduckgo‘ed for a long time and had a look at various image and file managing applications before finding gthumb. And even there, you first need to create a “catalog” and within the catalog a “library” which will finally allow you to manually sort your images. All of which is not documented.

Once you’ve sorted your images, you’d possibly want to export the sorting? Again, no trace of any help or documentation: gthumb catalogs are saved under $HOME/.local/share/gthumb/catalogs/foobar.catalog.

Tomáš Pospíšek

to visually sort images under Linux doesn’t seem to be a trivial task. I duckduckgo‘ed for a long time and had a look at various image and file managing applications before finding gthumb. And even there, you first need to create a “catalog” and within the catalog a “library” which will finally allow you to manually sort your images. All of which is not documented.

Once you’ve sorted your images, you’d possibly want to export the sorting? Again, no trace of any help or documentation: gthumb catalogs are saved under $HOME/.local/share/gthumb/catalogs/foobar.catalog.

Tomáš Pospíšek

Below is data from Randall Monroe’s Radiation Dose chart normalized to a year:

The spreadsheet with the data can be had here (in open document format (open office)) or in Excel format (don’t know if it renders well in Excel and others, since it was exported from open office).

Tomáš Pospíšek

Below is data from Randall Monroe’s Radiation Dose chart normalized to a year:

The spreadsheet with the data can be had here (in open document format (open office)) or in Excel format (don’t know if it renders well in Excel and others, since it was exported from open office).

Tomáš Pospíšek

Below is data from Randall Monroe’s Radiation Dose chart normalized to a year:

The spreadsheet with the data can be had here (in open document format (open office)) or in Excel format (don’t know if it renders well in Excel and others, since it was exported from open office).

Tomáš Pospíšek

A while ago I’ve compiled PostGIS 1.5.2 for PostgreSQL 9.0.

To install it on Ubuntu the following steps are required:

apt-get install python-software-properties

add-apt-repository ppa:ubuntugis/ubuntugis-unstable
add-apt-repository ppa:pitti/postgresql
add-apt-repository ppa:pi-deb/gis

apt-get update

apt-get install postgresql-9.0-postgis

A basic template database can be created with the following commands:

sudo su - postgres

createdb template_postgis
psql -q -d template_postgis -f /usr/share/postgresql/9.0/contrib/postgis-1.5/postgis.sql
psql -q -d template_postgis -f /usr/share/postgresql/9.0/contrib/postgis-1.5/spatial_ref_sys.sql
psql -q -d template_postgis -f /usr/share/postgresql/9.0/contrib/postgis_comments.sql
cat <<EOS | psql -d template_postgis
UPDATE pg_database SET datistemplate = TRUE WHERE datname = 'template_postgis';
REVOKE ALL ON SCHEMA public FROM public;
GRANT USAGE ON SCHEMA public TO public;
GRANT ALL ON SCHEMA public TO postgres;
GRANT SELECT, UPDATE, INSERT, DELETE
  ON TABLE public.geometry_columns TO PUBLIC;
GRANT SELECT, UPDATE, INSERT, DELETE
  ON TABLE public.spatial_ref_sys TO PUBLIC;
EOS

To test database creation you can do the following:

createdb --template template_postgis test_gis
psql -d test_gis -c "select postgis_lib_version();"

Ubuntu supports parallel installations of different PostgreSQL versions. So if you have already PostgreSQL 8.x installed, PostgreSQL 9.0 will probably be configured to listen on port 5433. So you have to add the option -p 5433 to each command and to specify the full path for the executables. For example:

/usr/lib/postgresql/9.0/bin/psql -p 5433 -d test_gis -c "select postgis_lib_version();"

A while ago I’ve compiled PostGIS 1.5.2 for PostgreSQL 9.0.

To install it on Ubuntu the following steps are required:

apt-get install python-software-properties

add-apt-repository ppa:ubuntugis/ubuntugis-unstable
add-apt-repository ppa:pitti/postgresql
add-apt-repository ppa:pi-deb/gis

apt-get update

apt-get install postgresql-9.0-postgis

A basic template database can be created with the following commands:

sudo su - postgres

createdb template_postgis
psql -q -d template_postgis -f /usr/share/postgresql/9.0/contrib/postgis-1.5/postgis.sql
psql -q -d template_postgis -f /usr/share/postgresql/9.0/contrib/postgis-1.5/spatial_ref_sys.sql
psql -q -d template_postgis -f /usr/share/postgresql/9.0/contrib/postgis_comments.sql
cat <<EOS | psql -d template_postgis
UPDATE pg_database SET datistemplate = TRUE WHERE datname = 'template_postgis';
REVOKE ALL ON SCHEMA public FROM public;
GRANT USAGE ON SCHEMA public TO public;
GRANT ALL ON SCHEMA public TO postgres;
GRANT SELECT, UPDATE, INSERT, DELETE
  ON TABLE public.geometry_columns TO PUBLIC;
GRANT SELECT, UPDATE, INSERT, DELETE
  ON TABLE public.spatial_ref_sys TO PUBLIC;
EOS

To test database creation you can do the following:

createdb --template template_postgis test_gis
psql -d test_gis -c "select postgis_lib_version();"

Ubuntu supports parallel installations of different PostgreSQL versions. So if you have already PostgreSQL 8.x installed, PostgreSQL 9.0 will probably be configured to listen on port 5433. So you have to add the option -p 5433 to each command and to specify the full path for the executables. For example:

/usr/lib/postgresql/9.0/bin/psql -p 5433 -d test_gis -c "select postgis_lib_version();"

A short visit and 7 hours train ride to the OpenLayers code sprint mainly for a presentation at the Swiss MapFish user group meeting in Lausanne, resulted in a new release of the QGIS OpenLayers plugin. The OpenLayers plugin adds WebKit based layers to QGIS and ships with OpenStreetMap-, Google- and Yahoo-Layers.

Changes in this release:

• Update to OpenLayers trunk
• Google Layers using API V3 (no API key necessary)
• Code refactoring for adding new layer types with one line of code (and some HTML…)

The next planned step is integrating this plugin with the very nice Openlayers Overview plugin from Luiz Motta.

Information for adding your own layers and a bug tracker is now available at hub.qgis.org/projects/openlayers

QGIS server is already known as a full featured, WMS 1.3 compliant map server (see e.g. ETHZ, Linfiniti or 3LIZ).

For the city of Uster, Switzerland, Sourcepole recently extended QGIS server with the possibility to use the print composer via WMS in order to offer printing functionality for web maps. A very nice GeoExt based client can be found at http://gis.uster.ch/webgis/. Andreas Neumann used and extended the GeoExt PrintProvider and PrintExtent classes which allows the user to intuitively select a layout, extent, scale, rotation and resolution for printing. The widget then sends a GetPrint request to QGIS server and a printable PDF is returned.

Now to the technical details: in order to use the print capability of QGIS server, the published project needs to contain one or more print compositions. QGIS server includes information about the available composer templates in the GetCapabilities response:

<WMS_Capabilities>
...
<ComposerTemplates xsi:type="wms:_ExtendedCapabilities">
<ComposerTemplate width="297" height="210" name="Composer 1">
<ComposerMap width="102" height="95" name="map0"/>
<ComposerMap width="133" height="79.87912087912088" name="map1"/>
<ComposerLabel name="hello_world"/>
</ComposerTemplate>
</ComposerTemplates>
...

With a 'GetPrint' request, the client may now request printable output in png or pdf format. The client needs to select an available composer template and needs to pass the selected extents for the composer maps. Additionally, there is the possibility to replace the text of composer labels. An example for a 'GetPrint' request is (note the new 'TEMPLATE' and 'map0:extent' Parameters):

http://localhost/fcgi-bin/qgis_mapserver/qgis_mapserv.fcgi?MAP=/home/marco/geodaten/projekte/composertest.qgs&SERVICE;=WMS&VERSION;=1.3.0&REQUEST;=GetPrint&TEMPLATE;=Composer 1&map0;:extent=693457.466131,227122.338236,700476.845177,230609.807051&BBOX;=693457.466131,227122.338236,700476.845177,230609.807051&CRS;=EPSG:21781&WIDTH;=1467&HEIGHT;=729&LAYERS;=layer0,layer1&STYLES;=,&FORMAT;=pdf&DPI;=300&TRANSPARENT;=true

• <mapname>:EXTENT=<xmin,ymin,xmax, ymax> //mandatory
• <mapname>:ROTATION=<double> //optional, defaults to 0
• <mapname>:SCALE=<double> //optional. Forces scale denominator as server and client may have different scale calculations
• <mapname>:LAYERS=<comma separated list with layer names> //optional. Defaults to all layer in the WMS request
• <mapname>:STYLES=<comma separated list with style names> //optional
• <mapname>:GRID_INTERVAL_X=<double> //set the grid interval in x-direction for composer grids
• <mapname>:GRID_INTERVAL_Y=<double> //set the grid interval in x-direction for composer grids

To replace text in composer labels, the label needs to have a text id (can be assigned in the print composer user interface of the composer label). The text to insert into the label can be passed in the GetPrint request with an additional parameter =text (of course, the label id should be different to the standard WMS parameters...).

Besides printing, an additional nice feature in the most recent developer version is the possibility to also use relative pathes in published project files. Like this, it's possible to conveniently export a project file recursively together with the corresponding data.

Finally, I'd like to thank the city of Uster and Andreas Neumann for the generous support and the creative ideas during the implementation of the printing functionality.

This is a short series of howtos for and a critique of JMeter v2.4.

The following articles have been done:

• Some words on overall usefulnes of JMeter
• The JMeter “Workbench”, a trapdoor for the newbie
• Debugging JMeter Tests
• Making your JMeter Test modular
• Working with big files/calling external scripts in JMeter
• Extracting text from a page and using it somewhere else in JMeter
• Waiting for a page change in JMeter

Tomáš Pospíšek, 4.1.2011

(This article is part of the JMeter Series)

JMeter’s “HTTP Request Sampler” will read the whole input (the downloaded page, pdf, movie etc.) into its main memory. That means that working with larger (f.ex. movies) files will bring JMeter, the JVM and/or many machines to their memory limits.

If you do not not need to do more than making sure that something gets downloaded, then you can “offload” the download work to an outside process, f.ex. to curl or wget:

A few things to note:

• I used the “BeanShell Sampler” module, since both the “BeanShell Pre-” and the “PostProcessors” are only executed when there’s something to process after another sampler produced some data.

• As you can see, we are passing a JMeter variable to the script

• Aparently JMeter or the BeanShell do not care much about the output of the exec’ed script, thus you won’t see anything inside the “Response data” in the “View Results Tree Sampler”. I don’t know whether that behaveour is a missing feature, a bug or for some unknown reason intended as such.

You can download this JMeter test from here

Tomáš Pospíšek, 30.12.2010

(This article is part of the JMeter Series)

While testing a Rails application there was a situation where a background worker (DJB or background task) would get an order to execute and eventually the completed order would appear on a page.

Thus we needed to wait for the page to be updated and continue the test after.

User Defined Variables

I’m predefining used variables here - see “We set up our variables” in the Extracting text from a page and using it somewhere else in JMeter article for an exaplanation why.

Clear Loop Variable

This step is not strictly necessary in our example here, however if you want to reuse this sequence of steps more than one time - that is call it from different places, then you need to clear the loop variable first.

Debug

Since creating these steps was not easy, I’ve put a debug statement in so that I see, when JMeter calls into these steps and to see how the variables are set.

The While Controler

Here we really start the loop.

I’m not sure whether if would be better to use BeanShell commands here instead - using JavaScript to test the loop condition works in any case…

Getting the page

We get the page we want to check.

Extract the data we want to check from the page and assign it to our loop variable

Make sure our request is not being cached

It’s better - as far as we can - to be sure we force the web application to recreate the page we’re waiting for to change. I’m not sure I’ve done it right here, however it works:

Wait a bit before re-looping

We wait two seconds here before retrying.

You can download this JMeter test from here

Tomáš Pospíšek, 4.1.2011

(This article is part of the JMeter Series)

In the following we’ll do these things:

1. we go to a form submit page
2. we order something
3. we get that something we ordered

In more detail:

We use a “Cookie Manager” to carry forward cookies between calls

We set up our variables

The idea here being that we predefine the variables, so they would show up in the “Debug Sampler” which makes debugging easier, because you see at each step, whether the variable has the correct value or not. I do predefine the variables with a “non-value” so that I can see immediately whether the variable has been already assigned something during the execution of the test or not.

We go to a form submit page

We extract the AUTHTOKEN from that form

(The auth token is being used by the web application to prevent cross-site-scripting)

Notice that the extractor is set to extract the string from the HTTP reply-body.

We also extract the session cookie

This is because we want to pass the cookie to an outside application, so that it can call the web app from within the same session.

Notice that this time we told the extractor to extract the string from the HTTP reply-headers.

We now use all our extracted parameters to submit our order

Note that:

• we are passing the AUTHTOKEN along with the HTTP POST
• since we are not sure whether possibly the AUTHTOKEN contains some problematic character (in my case it was an equal sign ‘=’ that was interferring with the parameter encoding) we tell JMeter to URL-encode the string.
• we also pass along another parameter telling the web app what we’re interested in getting back from our order
• we are using HTTPS

Submitting the order will redirect us to the page that’ll show us the resulting order.

We extract the ORDER_ID from HTTP headers which would otherwise redirect us to the resulting page

The headers contain the location of the resulting order page where we would be redirected to.

Finally we download the resulting artefact with curl

Note that:

• we are passing the SESSION_COOKIE to curl to be able to download the artifact in the same (potentially authenticated) session.

• we also construct the download URL from the ORDER_ID

You can download this JMeter test from here

Tomáš Pospíšek, 4.1.2011