Simplified GetWindowScaleDPI() so it does not fetch the wrong DPI scale some times (Windows looks at center of window while the old raylib code looked on upper left corner of window, now it just uses the glfw function to fetch the window's current scaling). Also introduced a callback to update the CORE.Window.screenScaling when the content scaling updates, previously scaling did not work correctly on systems with multiple monitors that have different DPI scaling. (#3701)

src/platforms/rcore_desktop.c

@@ -123,6 +123,7 @@ static void WindowIconifyCallback(GLFWwindow *window, int iconified);
 static void WindowMaximizeCallback(GLFWwindow* window, int maximized);                     // GLFW3 Window Maximize Callback, runs when window is maximized
 static void WindowFocusCallback(GLFWwindow *window, int focused);                          // GLFW3 WindowFocus Callback, runs when window get/lose focus
 static void WindowDropCallback(GLFWwindow *window, int count, const char **paths);         // GLFW3 Window Drop Callback, runs when drop files into window
+static void WindowContentScaleCallback(GLFWwindow *window, float scalex, float scaley);    // GLFW3 Window Content Scale Callback, runs when window changes scale
 
 // Input callbacks events
 static void KeyCallback(GLFWwindow *window, int key, int scancode, int action, int mods);  // GLFW3 Keyboard Callback, runs on key pressed
@@ -941,31 +942,8 @@ Vector2 GetWindowPosition(void)
 // Get window scale DPI factor for current monitor
 Vector2 GetWindowScaleDPI(void)
 {
-    float xdpi = 1.0;
+    Vector2 scale = {0};
-    float ydpi = 1.0;
+    glfwGetWindowContentScale(platform.handle, &scale.x, &scale.y);
-    Vector2 scale = { 1.0f, 1.0f };
-    Vector2 windowPos = GetWindowPosition();
-
-    int monitorCount = 0;
-    GLFWmonitor **monitors = glfwGetMonitors(&monitorCount);
-
-    // Check window monitor
-    for (int i = 0; i < monitorCount; i++)
-    {
-        glfwGetMonitorContentScale(monitors[i], &xdpi, &ydpi);
-
-        int xpos, ypos, width, height;
-        glfwGetMonitorWorkarea(monitors[i], &xpos, &ypos, &width, &height);
-
-        if ((windowPos.x >= xpos) && (windowPos.x < xpos + width) &&
-            (windowPos.y >= ypos) && (windowPos.y < ypos + height))
-        {
-            scale.x = xdpi;
-            scale.y = ydpi;
-            break;
-        }
-    }
-
     return scale;
 }
 
@@ -1553,6 +1531,11 @@ int InitPlatform(void)
     glfwSetWindowFocusCallback(platform.handle, WindowFocusCallback);
     glfwSetDropCallback(platform.handle, WindowDropCallback);
 
+    if ((CORE.Window.flags & FLAG_WINDOW_HIGHDPI) > 0)
+    {
+       glfwSetWindowContentScaleCallback(platform.handle, WindowContentScaleCallback);
+    }
+
     // Set input callback events
     glfwSetKeyCallback(platform.handle, KeyCallback);
     glfwSetCharCallback(platform.handle, CharCallback);
@@ -1638,6 +1621,11 @@ static void WindowSizeCallback(GLFWwindow *window, int width, int height)
     // NOTE: Postprocessing texture is not scaled to new size
 }
 
+static void WindowContentScaleCallback(GLFWwindow *window, float scalex, float scaley)
+{
+    CORE.Window.screenScale = MatrixScale(scalex, scaley, 1.0f);
+}
+
 // GLFW3 WindowIconify Callback, runs when window is minimized/restored
 static void WindowIconifyCallback(GLFWwindow *window, int iconified)
 {

src/platforms/rcore_web.c

@@ -115,6 +115,7 @@ static void WindowIconifyCallback(GLFWwindow *window, int iconified);
 //static void WindowMaximizeCallback(GLFWwindow *window, int maximized);                // GLFW3 Window Maximize Callback, runs when window is maximized
 static void WindowFocusCallback(GLFWwindow *window, int focused);                       // GLFW3 WindowFocus Callback, runs when window get/lose focus
 static void WindowDropCallback(GLFWwindow *window, int count, const char **paths);      // GLFW3 Window Drop Callback, runs when drop files into window
+static void WindowContentScaleCallback(GLFWwindow *window, float scalex, float scaley); // GLFW3 Window Content Scale Callback, runs when window changes scale
 
 // Input callbacks events
 static void KeyCallback(GLFWwindow *window, int key, int scancode, int action, int mods); // GLFW3 Keyboard Callback, runs on key pressed
@@ -1190,6 +1191,11 @@ int InitPlatform(void)
     glfwSetWindowFocusCallback(platform.handle, WindowFocusCallback);
     glfwSetDropCallback(platform.handle, WindowDropCallback);
 
+    if ((CORE.Window.flags & FLAG_WINDOW_HIGHDPI) > 0)
+    {
+       glfwSetWindowContentScaleCallback(platform.handle, WindowContentScaleCallback);
+    }
+
     // Set input callback events
     glfwSetKeyCallback(platform.handle, KeyCallback);
     glfwSetCharCallback(platform.handle, CharCallback);
@@ -1327,6 +1333,11 @@ static void WindowSizeCallback(GLFWwindow *window, int width, int height)
     // NOTE: Postprocessing texture is not scaled to new size
 }
 
+static void WindowContentScaleCallback(GLFWwindow *window, float scalex, float scaley)
+{
+    CORE.Window.screenScale = MatrixScale(scalex, scaley, 1.0f);
+}
+
 // GLFW3 WindowIconify Callback, runs when window is minimized/restored
 static void WindowIconifyCallback(GLFWwindow *window, int iconified)
 {