Zoom Tool

In Qwt6, QwtPlotZoomer required specifying two axes for zoom operations. If your plot needed all four axes to work, you had to bind two zoomers to the plot:

// Qwt6 traditional usage - requires two zoomers to cover four axes
QwtPlotZoomer* zoomer1 = new QwtPlotZoomer(QwtAxis::XBottom, QwtAxis::YLeft, canvas);
QwtPlotZoomer* zoomer2 = new QwtPlotZoomer(QwtAxis::XTop, QwtAxis::YRight, canvas);

To solve this problem, the new version introduces the following refactoring:

• QwtPlotAxisZoomer - A rename of the original QwtPlotZoomer, representing a zoomer bound to two specific axes
• QwtPlotCanvasZoomer - A new zoomer that does not require specifying axes and performs overall zoom on the entire canvas

Zoomer Feature Comparison

Below is a feature comparison of these two zoomers:

Feature	QwtPlotAxisZoomer	QwtPlotCanvasZoomer
Axis Binding	Requires specifying X and Y axes	Automatically handles all four axes
Use Case	Specific axis zoom	Overall canvas zoom
Parasite Plot Support	Requires manual binding	Automatically supports all parasite plots

Usage Examples

QwtPlotAxisZoomer and QwtPlotCanvasZoomer have the same usage pattern, with the difference being that QwtPlotCanvasZoomer does not require specifying axes.

QwtPlotAxisZoomer Usage Example

#include "qwt_plot_axis_zoomer.h"

// Create a zoomer for specific axes
QwtPlotAxisZoomer* axisZoomer = new QwtPlotAxisZoomer(
    QwtAxis::XBottom,  // X axis
    QwtAxis::YLeft,    // Y axis
    plot->canvas(),            // Canvas
    true               // Auto repaint
);

// Or use default axes
QwtPlotAxisZoomer* defaultZoomer = new QwtPlotAxisZoomer(plot->canvas());

QwtPlotCanvasZoomer Usage Example

#include "qwt_plot_canvas_zoomer.h"

// Create overall canvas zoomer, automatically handles all axes
QwtPlotCanvasZoomer* canvasZoomer = new QwtPlotCanvasZoomer(plot->canvas());

Key Settings Description

Default Key Bindings

Mouse Operations

Operation	Default Button	Description
Zoom Selection	Left button drag	Select rectangular area for zooming
Back to Base	Right button click	Zoom to base view (fully zoomed out)
Step Back	Middle button click	Step back one zoom level
Step Forward	Middle+Shift click	Step forward one zoom level

Keyboard Operations

Operation	Default Key	Description
Step Forward	+	Step forward one zoom level
Step Back	-	Step back one zoom level
Back to Base	Escape	Return to base view

Custom Key Configuration

You can configure shortcuts using the following predefined button configurations.

The following mouse shortcuts are supported:
- MouseSelect2: Reset to base
- MouseSelect3: Zoom stack back
- MouseSelect6: Zoom stack forward

The following keyboard shortcuts are supported:
- KeyUndo: Zoom stack back
- KeyRedo: Zoom stack forward
- KeyHome: Reset to base

// Configure custom keys
zoomer->setKeyPattern(QwtEventPattern::KeyRedo, Qt::Key_Plus,Qt::ShiftModifier);    // Zoom stack forward (zoom in)
zoomer->setKeyPattern(QwtEventPattern::KeyUndo, Qt::Key_Minus,Qt::ShiftModifier);   // Zoom stack back (zoom out)
zoomer->setKeyPattern(QwtEventPattern::KeyHome, Qt::Key_Escape);  // Reset

// Configure mouse patterns, middle button becomes reset to base, right button becomes step back
zoomer->setMousePattern(QwtEventPattern::MouseSelect2, Qt::MiddleButton);
zoomer->setMousePattern(QwtEventPattern::MouseSelect3, Qt::RightButton);