Implement window transparency to mouse events (#1236)

include/GLFW/glfw3.h

@@ -832,6 +832,13 @@ extern "C" {
  */
 #define GLFW_FOCUS_ON_SHOW          0x0002000C
 
+/*! @brief Forward mouse input to window behind.
+ *
+ *  Mouse input forwarding[window hint](@ref GLFW_MOUSE_PASSTHRU_hint) or
+ *  [window attribute](@ref GLFW_MOUSE_PASSTHRU_attrib).
+ */
+#define GLFW_MOUSE_PASSTHRU         0x0002000D
+
 /*! @brief Framebuffer bit depth hint.
  *
  *  Framebuffer bit depth [hint](@ref GLFW_RED_BITS).
@@ -3499,6 +3506,7 @@ GLFWAPI int glfwGetWindowAttrib(GLFWwindow* window, int attrib);
  *  [GLFW_FLOATING](@ref GLFW_FLOATING_attrib),
  *  [GLFW_AUTO_ICONIFY](@ref GLFW_AUTO_ICONIFY_attrib) and
  *  [GLFW_FOCUS_ON_SHOW](@ref GLFW_FOCUS_ON_SHOW_attrib).
+ *  [GLFW_MOUSE_PASSTHRU](@ref GLFW_MOUSE_PASSTHRU_attrib)
  *
  *  Some of these attributes are ignored for full screen windows.  The new
  *  value will take effect if the window is later made windowed.

src/cocoa_window.m

@@ -1356,6 +1356,14 @@ void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled)
     } // autoreleasepool
 }
 
+void _glfwPlatformSetWindowMousePassthru(_GLFWwindow* window, GLFWbool enabled)
+{
+    window->mousePassthru = enabled;
+    @autoreleasepool {
+    [window->ns.object setIgnoresMouseEvents:enabled];
+    }
+}
+
 float _glfwPlatformGetWindowOpacity(_GLFWwindow* window)
 {
     @autoreleasepool {

src/internal.h

@@ -265,6 +265,7 @@ struct _GLFWwndconfig
     GLFWbool      maximized;
     GLFWbool      centerCursor;
     GLFWbool      focusOnShow;
+    GLFWbool      mousePassthru;
     GLFWbool      scaleToMonitor;
     struct {
         GLFWbool  retina;
@@ -372,6 +373,7 @@ struct _GLFWwindow
     GLFWbool            autoIconify;
     GLFWbool            floating;
     GLFWbool            focusOnShow;
+    GLFWbool            mousePassthru;
     GLFWbool            shouldClose;
     void*               userPointer;
     GLFWvidmode         videoMode;
@@ -669,6 +671,7 @@ float _glfwPlatformGetWindowOpacity(_GLFWwindow* window);
 void _glfwPlatformSetWindowResizable(_GLFWwindow* window, GLFWbool enabled);
 void _glfwPlatformSetWindowDecorated(_GLFWwindow* window, GLFWbool enabled);
 void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled);
+void _glfwPlatformSetWindowMousePassthru(_GLFWwindow* window, GLFWbool enabled);
 void _glfwPlatformSetWindowOpacity(_GLFWwindow* window, float opacity);
 
 void _glfwPlatformPollEvents(void);

src/null_window.c

@@ -189,6 +189,10 @@ void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled)
 {
 }
 
+void _glfwPlatformSetWindowMousePassthru(_GLFWwindow* window, GLFWbool enabled)
+{
+}
+
 float _glfwPlatformGetWindowOpacity(_GLFWwindow* window)
 {
     return 1.f;

src/win32_window.c

@@ -1195,6 +1195,13 @@ static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg,
             DragFinish(drop);
             return 0;
         }
+
+        case WM_NCHITTEST:
+        {
+            if (window->mousePassthru)
+                return HTTRANSPARENT;
+            break;
+        }
     }
 
     return DefWindowProcW(hWnd, uMsg, wParam, lParam);
@@ -1847,6 +1854,11 @@ void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled)
                  SWP_NOACTIVATE | SWP_NOMOVE | SWP_NOSIZE);
 }
 
+void _glfwPlatformSetWindowMousePassthru(_GLFWwindow* window, GLFWbool enabled)
+{
+    window->mousePassthru = enabled;
+}
+
 float _glfwPlatformGetWindowOpacity(_GLFWwindow* window)
 {
     BYTE alpha;

src/window.c

@@ -243,6 +243,8 @@ GLFWAPI GLFWwindow* glfwCreateWindow(int width, int height,
         }
     }
 
+    _glfwPlatformSetWindowMousePassthru(window, wndconfig.mousePassthru);
+
     return (GLFWwindow*) window;
 }
 
@@ -375,6 +377,9 @@ GLFWAPI void glfwWindowHint(int hint, int value)
         case GLFW_FOCUS_ON_SHOW:
             _glfw.hints.window.focusOnShow = value ? GLFW_TRUE : GLFW_FALSE;
             return;
+        case GLFW_MOUSE_PASSTHRU:
+            _glfw.hints.window.mousePassthru = value ? GLFW_TRUE : GLFW_FALSE;
+            return;
         case GLFW_CLIENT_API:
             _glfw.hints.context.client = value;
             return;
@@ -819,6 +824,8 @@ GLFWAPI int glfwGetWindowAttrib(GLFWwindow* handle, int attrib)
             return _glfwPlatformWindowHovered(window);
         case GLFW_FOCUS_ON_SHOW:
             return window->focusOnShow;
+        case GLFW_MOUSE_PASSTHRU:
+            return window->mousePassthru;
         case GLFW_TRANSPARENT_FRAMEBUFFER:
             return _glfwPlatformFramebufferTransparent(window);
         case GLFW_RESIZABLE:
@@ -897,6 +904,8 @@ GLFWAPI void glfwSetWindowAttrib(GLFWwindow* handle, int attrib, int value)
     }
     else if (attrib == GLFW_FOCUS_ON_SHOW)
         window->focusOnShow = value;
+    else if (attrib == GLFW_MOUSE_PASSTHRU)
+        _glfwPlatformSetWindowMousePassthru(window, value);
     else
         _glfwInputError(GLFW_INVALID_ENUM, "Invalid window attribute 0x%08X", attrib);
 }

src/wl_window.c

@@ -1140,6 +1140,23 @@ void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled)
                     "Wayland: Window attribute setting not implemented yet");
 }
 
+void _glfwPlatformSetWindowMousePassthru(_GLFWwindow* window, GLFWbool enabled)
+{
+    if (enabled == window->mousePassthru)
+        return;
+
+    if (enabled)
+    {
+        struct wl_region* region = wl_compositor_create_region(_glfw.wl.compositor);
+        wl_surface_set_input_region(window->wl.surface, region);
+        wl_region_destroy(region);
+    }
+    else
+        wl_surface_set_input_region(window->wl.surface, 0);
+    wl_surface_commit(window->wl.surface);
+    window->mousePassthru = enabled;
+}
+
 float _glfwPlatformGetWindowOpacity(_GLFWwindow* window)
 {
     return 1.f;

src/x11_init.c

@@ -707,6 +707,33 @@ static GLFWbool initExtensions(void)
         }
     }
 
+#if defined(__CYGWIN__)
+    _glfw.x11.xshape.handle = _glfw_dlopen("libXext-6.so");
+#else
+    _glfw.x11.xshape.handle = _glfw_dlopen("libXext.so.6");
+#endif
+    if (_glfw.x11.xshape.handle)
+    {
+        _glfw.x11.xshape.QueryExtension = (PFN_XShapeQueryExtension)
+            _glfw_dlsym(_glfw.x11.xshape.handle, "XShapeQueryExtension");
+        _glfw.x11.xshape.ShapeCombineRegion = (PFN_XShapeCombineRegion)
+            _glfw_dlsym(_glfw.x11.xshape.handle, "XShapeCombineRegion");
+        _glfw.x11.xshape.QueryVersion = (PFN_XShapeQueryVersion)
+            _glfw_dlsym(_glfw.x11.xshape.handle, "XShapeQueryVersion");
+
+        if (XShapeQueryExtension(_glfw.x11.display,
+            &_glfw.x11.xshape.errorBase,
+            &_glfw.x11.xshape.eventBase))
+        {
+            if (XShapeQueryVersion(_glfw.x11.display,
+                &_glfw.x11.xshape.major,
+                &_glfw.x11.xshape.minor))
+            {
+                _glfw.x11.xshape.available = GLFW_TRUE;
+            }
+        }
+    }
+
     // Update the key code LUT
     // FIXME: We should listen to XkbMapNotify events to track changes to
     // the keyboard mapping.

src/x11_platform.h

@@ -123,6 +123,13 @@ typedef XRenderPictFormat* (* PFN_XRenderFindVisualFormat)(Display*,Visual const
 #define XRenderQueryVersion _glfw.x11.xrender.QueryVersion
 #define XRenderFindVisualFormat _glfw.x11.xrender.FindVisualFormat
 
+typedef Bool (* PFN_XShapeQueryExtension)(Display*,int*,int*);
+typedef Status (* PFN_XShapeQueryVersion)(Display*dpy,int*,int*);
+typedef void (* PFN_XShapeCombineRegion)(Display*,Window,int,int,int,Region,int);
+#define XShapeQueryExtension _glfw.x11.xshape.QueryExtension
+#define XShapeQueryVersion _glfw.x11.xshape.QueryVersion
+#define XShapeCombineRegion _glfw.x11.xshape.ShapeCombineRegion
+
 typedef VkFlags VkXlibSurfaceCreateFlagsKHR;
 typedef VkFlags VkXcbSurfaceCreateFlagsKHR;
 
@@ -404,6 +411,18 @@ typedef struct _GLFWlibraryX11
         PFN_XRenderFindVisualFormat FindVisualFormat;
     } xrender;
 
+    struct {
+        GLFWbool    available;
+        void*       handle;
+        int         major;
+        int         minor;
+        int         eventBase;
+        int         errorBase;
+        PFN_XShapeQueryExtension QueryExtension;
+        PFN_XShapeCombineRegion ShapeCombineRegion;
+        PFN_XShapeQueryVersion QueryVersion;
+    } xshape;
+
 } _GLFWlibraryX11;
 
 // X11-specific per-monitor data

src/x11_window.c

@@ -2630,6 +2630,32 @@ void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled)
     XFlush(_glfw.x11.display);
 }
 
+void _glfwPlatformSetWindowMousePassthru(_GLFWwindow* window, GLFWbool enabled)
+{
+    if (!_glfw.x11.xshape.available)
+        return;
+
+    if (enabled == window->mousePassthru)
+        return;
+
+    int width = 0;
+    int height = 0;
+    if (!enabled)
+        _glfwPlatformGetWindowSize(window, &width, &height);
+
+    XRectangle rect;
+    rect.x = 0;
+    rect.y = 0;
+    rect.width = (unsigned short)width;
+    rect.height = (unsigned short)height;
+
+    Region region = XCreateRegion();
+    XUnionRectWithRegion(&rect, region, region);
+    XShapeCombineRegion(_glfw.x11.display, window->x11.handle, 2/*ShapeInput*/, 0, 0, region, 0/*ShapeSet*/);
+    XDestroyRegion(region);
+    window->mousePassthru = enabled;
+}
+
 float _glfwPlatformGetWindowOpacity(_GLFWwindow* window)
 {
     float opacity = 1.f;