LinuxComponentPeer: Fix scaling in custom windows created by plugins

Previously, things like PopupMenus which were created in their own
windows were not being scaled correctly on HiDPI displays on Linux.

This patch forces the display scale to 1.0 in plugins, meaning that
the transform applied to the main plugin window is the sole source
of truth for component scaling in plugins.

modules/juce_gui_basics/native/juce_linux_Windowing.cpp

@@ -85,8 +85,8 @@ public:
 
         updateScaleFactorFromNewBounds (bounds, false);
 
-        auto physicalBounds = (parentWindow == 0 ? Desktop::getInstance().getDisplays().logicalToPhysical (bounds)
-                               : bounds * currentScaleFactor);
+        auto physicalBounds = parentWindow == 0 ? Desktop::getInstance().getDisplays().logicalToPhysical (bounds)
+                                                : bounds * currentScaleFactor;
 
         WeakReference<Component> deletionChecker (&component);
 
@@ -103,13 +103,16 @@ public:
 
     Point<int> getScreenPosition (bool physical) const
     {
-        auto parentPosition = XWindowSystem::getInstance()->getParentScreenPosition();
+        auto physicalParentPosition = XWindowSystem::getInstance()->getPhysicalParentScreenPosition();
+        auto parentPosition = parentWindow == 0 ? Desktop::getInstance().getDisplays().physicalToLogical (physicalParentPosition)
+                                                : physicalParentPosition / currentScaleFactor;
 
-        auto screenBounds = (parentWindow == 0 ? bounds
-                                               : bounds.translated (parentPosition.x, parentPosition.y));
+        auto screenBounds = parentWindow == 0 ? bounds
+                                              : bounds.translated (parentPosition.x, parentPosition.y);
 
         if (physical)
-            return Desktop::getInstance().getDisplays().logicalToPhysical (screenBounds.getTopLeft());
+            return parentWindow == 0 ? Desktop::getInstance().getDisplays().logicalToPhysical (screenBounds.getTopLeft())
+                                     : screenBounds.getTopLeft() * currentScaleFactor;
 
         return screenBounds.getTopLeft();
     }
@@ -314,8 +317,8 @@ public:
 
             updateScaleFactorFromNewBounds (physicalBounds, true);
 
-            bounds = (parentWindow == 0 ? Desktop::getInstance().getDisplays().physicalToLogical (physicalBounds)
-                                        : physicalBounds / currentScaleFactor);
+            bounds = parentWindow == 0 ? Desktop::getInstance().getDisplays().physicalToLogical (physicalBounds)
+                                       : physicalBounds / currentScaleFactor;
         }
     }
 
@@ -433,9 +436,6 @@ private:
     //==============================================================================
     void updateScaleFactorFromNewBounds (const Rectangle<int>& newBounds, bool isPhysical)
     {
-        if (! JUCEApplicationBase::isStandaloneApp())
-            return;
-
         Point<int> translation = (parentWindow != 0 ? getScreenPosition (isPhysical) : Point<int>());
         const auto& desktop = Desktop::getInstance();
 

modules/juce_gui_basics/native/x11/juce_linux_XWindowSystem.cpp

@@ -1799,14 +1799,14 @@ Rectangle<int> XWindowSystem::getWindowBounds (::Window windowH, ::Window parent
         }
         else
         {
-            parentScreenPosition = Desktop::getInstance().getDisplays().physicalToLogical (Point<int> (rootX, rootY));
+            parentScreenPosition = Point<int> (rootX, rootY);
         }
     }
 
     return { wx, wy, (int) ww, (int) wh };
 }
 
-Point<int> XWindowSystem::getParentScreenPosition() const
+Point<int> XWindowSystem::getPhysicalParentScreenPosition() const
 {
     return parentScreenPosition;
 }
@@ -2424,7 +2424,7 @@ Array<Displays::Display> XWindowSystem::findDisplays (float masterScale) const
                                                   + ((static_cast<double> (crtc->height) * 25.4 * 0.5) / static_cast<double> (output->mm_height));
 
                                         auto scale = DisplayHelpers::getDisplayScale (output->name, d.dpi);
-                                        scale = (scale <= 0.1 ? 1.0 : scale);
+                                        scale = (scale <= 0.1 || ! JUCEApplicationBase::isStandaloneApp()) ? 1.0 : scale;
 
                                         d.scale = masterScale * scale;
 

modules/juce_gui_basics/native/x11/juce_linux_XWindowSystem.h

@@ -109,7 +109,7 @@ public:
 
     BorderSize<int> getBorderSize   (::Window) const;
     Rectangle<int>  getWindowBounds (::Window, ::Window parentWindow);
-    Point<int> getParentScreenPosition() const;
+    Point<int> getPhysicalParentScreenPosition() const;
 
     bool contains (::Window, Point<int> localPos) const;