# Walkthrough - Multi-Point Measurement Tool

The `ProfileMeasureTool` has been enhanced to support multi-point polyline measurements, allowing users to trace geological features along the profile and obtain comprehensive metrics. We have also added a dedicated "Finalizar" button to the UI for a robust and intuitive user experience.

## Features

### 1. Multi-Point Measurement
- **Sequential Clicks:** Users can click multiple times to define a polyline trace. Each click adds a new vertex.
- **Visual Feedback:** 
    - **Green Markers:** Added at each clicked point to clearly visualize the path.
    - **Red Rubber Band:** Connects the points dynamically.
    - **Live Preview:** A temporary line follows the mouse cursor to show where the next segment will be placed.

### 2. Comprehensive Metrics
The tool calculates and aggregates metrics for the entire polyline trace:
- **Total Distance:** Sum of 3D distances of all segments.
- **Horizontal Distance:** Total horizontal length projected on the profile.
- **Elevation Change:** Net difference between the first and last point (positive for gain, negative for loss).
- **Average Slope:** Calculated based on total elevation change over total horizontal distance.
- **Point & Segment Counts:** Displays the complexity of the trace.

### 3. Explicit Finalization
- **"Finalizar" Button:** A dedicated button appears in the UI (next to "Measure") when the tool is active.
- **Robust State:** Clicking "Finalizar":
    1.  **Completes the measurement.**
    2.  **Freezes the visual state:** The polyline and markers remain visible for reference.
    3.  **Shows final results:** The metrics panel displays the final calculated values.
    4.  **Prevents modification:** No further points can be added to the finished trace.
- **Auto-Reset:** activating the "Measure" button again automatically clears the previous measurement and starts a fresh one.

## Usage Flow

1.  **Activate Tool:** Click the **"Measure"** button in the Preview tab.
    - The cursor changes to a crosshair.
    - The **"Finalizar"** button appears next to "Measure".
    - Any previous measurement is cleared.
2.  **Trace Feature:** Click on the profile to place points along the feature you want to measure.
    - Green markers appear at each point.
    - Metrics update in real-time in the Results panel.
3.  **Complete Measurement:** Click the **"Finalizar"** button.
    - The measurement is finalized.
    - The temporary line following the cursor disappears.
    - The green markers and red polyline **remain visible**.
    - The final metrics are displayed in the Results panel.
    - The tool switches to Pan mode, but the measurement visuals persist.
4.  **New Measurement:** Click **"Measure"** again to start over.

## Implementation Details

### `ProfileMeasureTool` (`gui/tools/measure_tool.py`)
- **`points` & `finalized_points`**: Stores the list of measurement points. `finalized_points` preserves the data after finalization for display.
- **`finalized` flag**: Tracks whether the current measurement is complete to block further input.
- **`finalize_measurement()`**: 
    - Marks tool as finalized.
    - Saves points to `finalized_points`.
    - Updates metrics one last time.
    - **Switches to `QgsMapToolPan`**: This effectively "stops" the measuring interaction.
    - **Redraws Rubber Band**: Clears the dynamic rubber band and redraws it using static `finalized_points` to remove the temporary cursor line.
- **`reset()`**:
    - **If Finalized:** Clears only internal data (`points`) but **prevents** clearing the rubber band and markers, keeping the visual result on screen.
    - **If Not Finalized (or New Start):** Clears everything (data + visuals) for a fresh start.

### UI Integration (`gui/ui/pages/preview_page.py`, `gui/main_dialog.py`)
- **`btn_finalize`**: Added to the UI layout, initially hidden.
- **Visibility Logic**: `toggle_measure_tool` controls the visibility of the Finalize button (Show on Active, Hide on Inactive).
- **Signal Connection**: The button is connected to `measure_tool.finalize_measurement()`.

## Verification Results

### Functionality Tests
| Test Case | Expected Result | Status |
| :--- | :--- | :--- |
| **Activate Tool** | Cursor changes, "Finalizar" button appears, previous data clears. | ✅ Pass |
| **Add Points** | Points added, markers appear, rubber band updates, metrics update live. | ✅ Pass |
| **Finalize Measurement** | Tool stops, "Finalizar" button click works. | ✅ Pass |
| **Post-Finalization** | Visuals (line + markers) remain. Results text remains. No new points can be added. | ✅ Pass |
| **Restart Measurement** | Clicking "Measure" again clears old visuals/data and starts fresh. | ✅ Pass |
| **Async Geology** | Background geology processing completes without error (fixed `PreviewResult` import). | ✅ Pass |

### Metrics Accuracy
Confirms that multi-segment calculations correctly accumulate distance and handle positive/negative slope changes appropriately.
