Fix: Inaccurate mouse position in raylib WASM on web pages

Fixed an issue where the mouse position was inaccurate when the raylib library was compiled to WASM for web pages.

Problem Cause:
Upon investigation, the issue was determined to be caused by glfwSetCursorPosCallback (which is emulated in the WASM environment) returning the mouse position relative to the initial canvas size created during the InitWindow call. This means that even if the canvas element's size on the web page changed (e.g., after a window resize via CSS or JavaScript), glfwSetCursorPosCallback would still report mouse positions based on the original, fixed canvas dimensions. This led to incorrect mouse coordinates calculated by raylib's internals when the web page was not full-screen or when the Canvas element's size was dynamic.

src/platforms/rcore_web.c

@@ -1591,8 +1591,8 @@ static void MouseCursorPosCallback(GLFWwindow *window, double x, double y)
     // If the pointer is not locked, follow the position
     if (!CORE.Input.Mouse.cursorHidden)
     {
-        CORE.Input.Mouse.currentPosition.x = (float)x;
-        CORE.Input.Mouse.currentPosition.y = (float)y;
+        CORE.Input.Mouse.currentPosition.x = (float) x * CORE.Window.screen.width  / CORE.Window.initScreen.width;
+        CORE.Input.Mouse.currentPosition.y = (float) y * CORE.Window.screen.height / CORE.Window.initScreen.height;
         CORE.Input.Touch.position[0] = CORE.Input.Mouse.currentPosition;
     }
 

src/rcore.c

@@ -295,6 +295,7 @@ typedef struct CoreData {
         Point position;                     // Window position (required on fullscreen toggle)
         Point previousPosition;             // Window previous position (required on borderless windowed toggle)
         Size display;                       // Display width and height (monitor, device-screen, LCD, ...)
+        Size initScreen;                    // when init window, Screen width and height (used render area)
         Size screen;                        // Screen width and height (used render area)
         Size previousScreen;                // Screen previous width and height (required on borderless windowed toggle)
         Size currentFbo;                    // Current render width and height (depends on active fbo)
@@ -668,6 +669,9 @@ void InitWindow(int width, int height, const char *title)
     // Initialize window data
     CORE.Window.screen.width = width;
     CORE.Window.screen.height = height;
+    CORE.Window.initScreen.width = width;
+    CORE.Window.initScreen.height = height;
+
     CORE.Window.eventWaiting = false;
     CORE.Window.screenScale = MatrixIdentity();     // No draw scaling required by default
     if ((title != NULL) && (title[0] != 0)) CORE.Window.title = title;