[[ emscripten ]] Listen for device pixel ratio changes

livecode-vulcan · livecodeian · commit b3ee9f190e6e · 2021-06-30T09:55:32.000+01:00
This patch adds a listener for changes to the Window.devicePixelRatio
property, triggering a redraw of open stack windows at the new scale.
diff --git a/engine/src/em-event.js b/engine/src/em-event.js
@@ -130,6 +130,10 @@ mergeInto(LibraryManager.library, {
 				tInput.addEventListener(type, handler);
 			});
 
+			// Add listener for changes to device pixel ratio
+			var matchQuery = `(resolution: ${window.devicePixelRatio}dppx)`;
+			window.matchMedia(matchQuery).addListener(LiveCodeEvents._handleDevicePixelRatioChanged);
+
 			LiveCodeEvents._initialised = true;
 		},
 
@@ -892,6 +896,16 @@ mergeInto(LibraryManager.library, {
 		// UI events
 		// ----------------------------------------------------------------
 		
+		_handleDevicePixelRatioChanged: function() {
+			LiveCodeAsync.delay(function() {
+				Module.ccall('MCEmscriptenHandleDevicePixelRatioChanged',
+								'number', /* bool */
+								[],
+								[])
+			});
+			LiveCodeAsync.resume();
+		},
+
 		// prevent context menu popup on right-click
 		_handleContextMenu: function(e) {
 			e.preventDefault()
diff --git a/engine/src/em-resolution.cpp b/engine/src/em-resolution.cpp
@@ -16,12 +16,22 @@ for more details.
 You should have received a copy of the GNU General Public License
 along with LiveCode.  If not see <http://www.gnu.org/licenses/>.  */
 
+#include "globdefs.h"
+#include "filedefs.h"
+#include "osspec.h"
+#include "typedefs.h"
+#include "parsedef.h"
+#include "objdefs.h"
+
+#include "globals.h"
+
 #include "em-util.h"
 
 #include "sysdefs.h"
 
 #include "graphics.h"
 #include "resolution.h"
+#include "stacklst.h"
 
 #include <emscripten.h>
 
@@ -70,5 +80,19 @@ MCResPlatformGetUIDeviceScale()
 void
 MCResPlatformHandleScaleChange()
 {
-	MCEmscriptenNotImplemented();
+	// Global use-pixel-scaling value has been updated, so now we just need to reopen any open stack windows
+	MCstacks->reopenallstackwindows();
+}
+
+extern "C" MC_DLLEXPORT_DEF bool
+MCEmscriptenHandleDevicePixelRatioChanged()
+{
+	MCGFloat t_scale = emscripten_get_device_pixel_ratio();
+	if (t_scale != s_emscripten_device_scale)
+	{
+		s_emscripten_device_scale = t_scale;
+		MCResPlatformHandleScaleChange();
+	}
+
+	return true;
 }
