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[GTK] Use primary monitor for device zoom on multi-monitor setups #10

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[GTK] Use primary monitor for device zoom on multi-monitor setups #10

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16 changes: 15 additions & 1 deletion bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1107,7 +1107,7 @@ protected int getDeviceZoom() {
long surface = GTK4.gtk_native_get_surface(GTK4.gtk_widget_get_native(shellHandle));
monitor = GDK.gdk_display_get_monitor_at_surface(display, surface);
} else {
monitor = GDK.gdk_display_get_monitor_at_point(display, 0, 0);
monitor = getPrimaryMonitor(display);
}

// GDK can return null monitor in some cases thus play safe
Expand All @@ -1120,4 +1120,18 @@ protected int getDeviceZoom() {
return DPIUtil.mapDPIToZoom (dpi);
}

/**
* Returns the GDK primary monitor handle, falling back to the monitor at
* virtual coordinate (0,0) when no primary monitor is reported (e.g. on Wayland).
*
* @noreference This method is not intended to be referenced by clients.
*/
protected long getPrimaryMonitor(long display) {
long monitor = GDK.gdk_display_get_primary_monitor(display);
if (monitor == 0) {
monitor = GDK.gdk_display_get_monitor_at_point(display, 0, 0);
}
return monitor;
}

}
15 changes: 9 additions & 6 deletions bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2712,7 +2712,7 @@ public Monitor[] getMonitors() {
int scaleFactor = (int) GDK.gdk_monitor_get_scale_factor(gdkMonitor);
monitor.zoom = scaleFactor * 100;
} else {
monitor.zoom = Display._getDeviceZoom(monitor.handle);
monitor.zoom = _getDeviceZoom(monitor.handle);
}

/* workarea was defined in GTK 3.4. If present, it will return the best results
Expand Down Expand Up @@ -6256,16 +6256,19 @@ long gdk_device_get_surface_at_position (double[] win_x, double[] win_y) {
return GDK.gdk_device_get_surface_at_position (device, win_x, win_y);
}

static int _getDeviceZoom (long monitor_num) {
int _getDeviceZoom (long monitor) {
/*
* We can hard-code 96 as gdk_screen_get_resolution will always return -1
* if gdk_screen_set_resolution has not been called.
*/
int dpi = 96;
long display = GDK.gdk_display_get_default();
long monitor = GDK.gdk_display_get_monitor_at_point(display, 0, 0);
int scale = GDK.gdk_monitor_get_scale_factor(monitor);
dpi = dpi * scale;
if (monitor == 0) {
monitor = getPrimaryMonitor(GDK.gdk_display_get_default());
}
Comment on lines +6265 to +6267
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@gemini-code-assist gemini-code-assist Bot Apr 29, 2026

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medium

This logic for determining the default monitor is duplicated in Device.getDeviceZoom(). To improve maintainability, consider extracting this logic into a protected static helper method in the Device class and reusing it in both places.

For example, you could add the following method to Device.java:

protected static long getDefaultMonitor(long display) {
    long monitor = GDK.gdk_display_get_primary_monitor(display);
    if (monitor == 0) {
        monitor = GDK.gdk_display_get_monitor_at_point(display, 0, 0);
    }
    return monitor;
}

This new helper method could then be used here and in Device.getDeviceZoom() to simplify the code and remove the duplication.

if (monitor != 0) {
int scale = GDK.gdk_monitor_get_scale_factor(monitor);
dpi = dpi * scale;
}
return DPIUtil.mapDPIToZoom (dpi);
}

Expand Down
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