[rcore_web] Relative mouse mode issues. (#3940)

* [rcore_web] Relative mouse mode issues.

* Review formatting.

2 files changed, 36 insertions, 3 deletions

diff --git a/.gitignore b/.gitignore
index 6ff0e234..eeb1ed09 100644
--- a/.gitignore
+++ b/.gitignore
@@ -56,6 +56,9 @@ packages/
 *.so.*
 *.dll
 
+# Emscripten
+emsdk
+
 # Ignore wasm data in examples/
 examples/**/*.wasm
 examples/**/*.data
diff --git a/src/platforms/rcore_web.c b/src/platforms/rcore_web.c
index 9328b8c9..afe8adfb 100644
--- a/src/platforms/rcore_web.c
+++ b/src/platforms/rcore_web.c
@@ -100,6 +100,8 @@ static const char cursorLUT[11][12] = {
     "not-allowed"  // 10 MOUSE_CURSOR_NOT_ALLOWED
 };
 
+Vector2 lockedMousePos = { 0 };
+
 //----------------------------------------------------------------------------------
 // Module Internal Functions Declaration
 //----------------------------------------------------------------------------------
@@ -131,6 +133,7 @@ static EM_BOOL EmscriptenWindowResizedCallback(int eventType, const EmscriptenUi
 static EM_BOOL EmscriptenResizeCallback(int eventType, const EmscriptenUiEvent *event, void *userData);
 
 // Emscripten input callback events
+static EM_BOOL EmscriptenMouseMoveCallback(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData);
 static EM_BOOL EmscriptenMouseCallback(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData);
 static EM_BOOL EmscriptenPointerlockCallback(int eventType, const EmscriptenPointerlockChangeEvent *pointerlockChangeEvent, void *userData);
 static EM_BOOL EmscriptenTouchCallback(int eventType, const EmscriptenTouchEvent *touchEvent, void *userData);
@@ -862,6 +865,8 @@ void SetMousePosition(int x, int y)
     CORE.Input.Mouse.currentPosition = (Vector2){ (float)x, (float)y };
     CORE.Input.Mouse.previousPosition = CORE.Input.Mouse.currentPosition;
 
+    if (CORE.Input.Mouse.cursorHidden) lockedMousePos = CORE.Input.Mouse.currentPosition;
+
     // NOTE: emscripten not implemented
     glfwSetCursorPos(platform.handle, CORE.Input.Mouse.currentPosition.x, CORE.Input.Mouse.currentPosition.y);
 }
@@ -1270,6 +1275,9 @@ int InitPlatform(void)
     emscripten_set_click_callback("#canvas", NULL, 1, EmscriptenMouseCallback);
     emscripten_set_pointerlockchange_callback(EMSCRIPTEN_EVENT_TARGET_WINDOW, NULL, 1, EmscriptenPointerlockCallback);
 
+    // Following the mouse delta when the mouse is locked
+    emscripten_set_mousemove_callback("#canvas", NULL, 1, EmscriptenMouseMoveCallback);
+
     // Support touch events
     emscripten_set_touchstart_callback("#canvas", NULL, 1, EmscriptenTouchCallback);
     emscripten_set_touchend_callback("#canvas", NULL, 1, EmscriptenTouchCallback);
@@ -1477,9 +1485,13 @@ static void MouseButtonCallback(GLFWwindow *window, int button, int action, int
 // GLFW3 Cursor Position Callback, runs on mouse move
 static void MouseCursorPosCallback(GLFWwindow *window, double x, double y)
 {
-    CORE.Input.Mouse.currentPosition.x = (float)x;
-    CORE.Input.Mouse.currentPosition.y = (float)y;
-    CORE.Input.Touch.position[0] = CORE.Input.Mouse.currentPosition;
+    // 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.Touch.position[0] = CORE.Input.Mouse.currentPosition;
+    }
 
 #if defined(SUPPORT_GESTURES_SYSTEM) && defined(SUPPORT_MOUSE_GESTURES)
     // Process mouse events as touches to be able to use mouse-gestures
@@ -1505,6 +1517,18 @@ static void MouseCursorPosCallback(GLFWwindow *window, double x, double y)
 #endif
 }
 
+static EM_BOOL EmscriptenMouseMoveCallback(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData)
+{
+    // To emulate the GLFW_RAW_MOUSE_MOTION property.
+    if (CORE.Input.Mouse.cursorHidden)
+    {
+        CORE.Input.Mouse.previousPosition.x = lockedMousePos.x - mouseEvent->movementX;
+        CORE.Input.Mouse.previousPosition.y = lockedMousePos.y - mouseEvent->movementY;
+    }
+
+    return 1; // The event was consumed by the callback handler
+}
+
 // GLFW3 Scrolling Callback, runs on mouse wheel
 static void MouseScrollCallback(GLFWwindow *window, double xoffset, double yoffset)
 {
@@ -1598,6 +1622,12 @@ static EM_BOOL EmscriptenPointerlockCallback(int eventType, const EmscriptenPoin
 {
     CORE.Input.Mouse.cursorHidden = EM_ASM_INT( { if (document.pointerLockElement) return 1; }, 0);
 
+    if (CORE.Input.Mouse.cursorHidden)
+    {
+        lockedMousePos = CORE.Input.Mouse.currentPosition;
+        CORE.Input.Mouse.previousPosition = lockedMousePos;
+    }
+
     return 1; // The event was consumed by the callback handler
 }