Backport PR #28451: Fix GTK cairo backends

ksunden · meeseeksmachine · commit c43313a77ccb · 2024-07-03T20:09:13.000Z
diff --git a/lib/matplotlib/backends/backend_gtk3cairo.py b/lib/matplotlib/backends/backend_gtk3cairo.py
@@ -13,15 +13,19 @@ def on_draw_event(self, widget, ctx):
 
         with (self.toolbar._wait_cursor_for_draw_cm() if self.toolbar
               else nullcontext()):
-            self._renderer.set_context(ctx)
-            scale = self.device_pixel_ratio
-            # Scale physical drawing to logical size.
-            ctx.scale(1 / scale, 1 / scale)
             allocation = self.get_allocation()
+            # Render the background before scaling, as the allocated size here is in
+            # logical pixels.
             Gtk.render_background(
                 self.get_style_context(), ctx,
-                allocation.x, allocation.y,
-                allocation.width, allocation.height)
+                0, 0, allocation.width, allocation.height)
+            scale = self.device_pixel_ratio
+            # Scale physical drawing to logical size.
+            ctx.scale(1 / scale, 1 / scale)
+            self._renderer.set_context(ctx)
+            # Set renderer to physical size so it renders in full resolution.
+            self._renderer.width = allocation.width * scale
+            self._renderer.height = allocation.height * scale
             self._renderer.dpi = self.figure.dpi
             self.figure.draw(self._renderer)
 
diff --git a/lib/matplotlib/backends/backend_gtk4.py b/lib/matplotlib/backends/backend_gtk4.py
@@ -34,7 +34,6 @@ class FigureCanvasGTK4(_FigureCanvasGTK, Gtk.DrawingArea):
     required_interactive_framework = "gtk4"
     supports_blit = False
     manager_class = _api.classproperty(lambda cls: FigureManagerGTK4)
-    _context_is_scaled = False
 
     def __init__(self, figure=None):
         super().__init__(figure=figure)
@@ -228,13 +227,8 @@ def _post_draw(self, widget, ctx):
 
         lw = 1
         dash = 3
-        if not self._context_is_scaled:
-            x0, y0, w, h = (dim / self.device_pixel_ratio
-                            for dim in self._rubberband_rect)
-        else:
-            x0, y0, w, h = self._rubberband_rect
-            lw *= self.device_pixel_ratio
-            dash *= self.device_pixel_ratio
+        x0, y0, w, h = (dim / self.device_pixel_ratio
+                        for dim in self._rubberband_rect)
         x1 = x0 + w
         y1 = y0 + h
 
diff --git a/lib/matplotlib/backends/backend_gtk4cairo.py b/lib/matplotlib/backends/backend_gtk4cairo.py
@@ -5,7 +5,10 @@
 
 
 class FigureCanvasGTK4Cairo(FigureCanvasCairo, FigureCanvasGTK4):
-    _context_is_scaled = True
+    def _set_device_pixel_ratio(self, ratio):
+        # Cairo in GTK4 always uses logical pixels, so we don't need to do anything for
+        # changes to the device pixel ratio.
+        return False
 
     def on_draw_event(self, widget, ctx):
         if self._idle_draw_id:
@@ -16,15 +19,11 @@ def on_draw_event(self, widget, ctx):
         with (self.toolbar._wait_cursor_for_draw_cm() if self.toolbar
               else nullcontext()):
             self._renderer.set_context(ctx)
-            scale = self.device_pixel_ratio
-            # Scale physical drawing to logical size.
-            ctx.scale(1 / scale, 1 / scale)
             allocation = self.get_allocation()
             Gtk.render_background(
                 self.get_style_context(), ctx,
                 allocation.x, allocation.y,
                 allocation.width, allocation.height)
-            self._renderer.dpi = self.figure.dpi
             self.figure.draw(self._renderer)
 
 
