Fix lag on events

Found on sanctum2, returning 0 in XPending & XEventsQueued make the SDL do something else than polling events and makes lag the event loop.
Now the event loop returns 0 when there are no more events.

ImGui/impls/linux/imgui_impl_x11.cpp

@@ -23,8 +23,9 @@
 
 // X11 Data
 static Display*             g_Display = nullptr;
-static uint64_t              g_Time = 0;
+static Window               g_Window = 0;
-static uint64_t              g_TicksPerSecond = 0;
+static uint64_t             g_Time = 0;
+static uint64_t             g_TicksPerSecond = 0;
 static ImGuiMouseCursor     g_LastMouseCursor = ImGuiMouseCursor_COUNT;
 static bool                 g_HasGamepad = false;
 static bool                 g_WantUpdateHasGamepad = true;
@@ -56,7 +57,7 @@ bool IsKeySys(int key)
 }
 
 // Functions
-bool    ImGui_ImplX11_Init(void *display)
+bool    ImGui_ImplX11_Init(void *display, void *window)
 {
     timespec ts, tsres;
     clock_getres(CLOCK_MONOTONIC_RAW, &tsres);
@@ -72,6 +73,7 @@ bool    ImGui_ImplX11_Init(void *display)
 
     // Setup back-end capabilities flags
     g_Display = reinterpret_cast<Display*>(display);
+    g_Window = reinterpret_cast<Window>(window);
     ImGuiIO& io = ImGui::GetIO();
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;         // We can honor GetMouseCursor() values (optional)
     io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;          // We can honor io.WantSetMousePos requests (optional, rarely used)
@@ -107,6 +109,7 @@ bool    ImGui_ImplX11_Init(void *display)
 void    ImGui_ImplX11_Shutdown()
 {
     g_Display = nullptr;
+    g_Window = 0;
 }
 
 static bool ImGui_ImplX11_UpdateMouseCursor()
@@ -143,7 +146,7 @@ static bool ImGui_ImplX11_UpdateMouseCursor()
     return true;
 }
 
-static void ImGui_ImplX11_UpdateMousePos(Window window)
+static void ImGui_ImplX11_UpdateMousePos()
 {
     ImGuiIO& io = ImGui::GetIO();
 
@@ -160,7 +163,7 @@ static void ImGui_ImplX11_UpdateMousePos(Window window)
     int rx, ry, x, y;
     unsigned int mask;
 
-    XQueryPointer(g_Display, window, &unused_window, &unused_window, &rx, &ry, &x, &y, &mask);
+    XQueryPointer(g_Display, g_Window, &unused_window, &unused_window, &rx, &ry, &x, &y, &mask);
 
     io.MousePos.x = x;
     io.MousePos.y = y;
@@ -215,7 +218,7 @@ static void ImGui_ImplX11_UpdateGamepads()
     */
 }
 
-void    ImGui_ImplX11_NewFrame(void* window)
+void    ImGui_ImplX11_NewFrame()
 {
     ImGuiIO& io = ImGui::GetIO();
     IM_ASSERT(io.Fonts->IsBuilt() && "Font atlas not built! It is generally built by the renderer back-end. Missing call to renderer _NewFrame() function? e.g. ImGui_ImplOpenGL3_NewFrame().");
@@ -225,7 +228,7 @@ void    ImGui_ImplX11_NewFrame(void* window)
     int unused_int;
     unsigned int unused_unsigned_int;
 
-    XGetGeometry(g_Display, (Window)window, &unused_window, &unused_int, &unused_int, &width, &height, &unused_unsigned_int, &unused_unsigned_int);
+    XGetGeometry(g_Display, (Window)g_Window, &unused_window, &unused_int, &unused_int, &width, &height, &unused_unsigned_int, &unused_unsigned_int);
 
     io.DisplaySize.x = width;
     io.DisplaySize.y = height;
@@ -249,7 +252,7 @@ void    ImGui_ImplX11_NewFrame(void* window)
     // io.KeysDown[], io.MousePos, io.MouseDown[], io.MouseWheel: filled by the WndProc handler below.
 
     // Update OS mouse position
-    ImGui_ImplX11_UpdateMousePos((Window)window);
+    ImGui_ImplX11_UpdateMousePos();
     /*
     // Update OS mouse cursor with the cursor requested by imgui
     ImGuiMouseCursor mouse_cursor = io.MouseDrawCursor ? ImGuiMouseCursor_None : ImGui::GetMouseCursor();

ImGui/impls/linux/imgui_impl_x11.h

@@ -9,9 +9,9 @@
 
 #pragma once
 
-IMGUI_IMPL_API bool     ImGui_ImplX11_Init(void* display);
+IMGUI_IMPL_API bool     ImGui_ImplX11_Init(void* display, void* window);
 IMGUI_IMPL_API void     ImGui_ImplX11_Shutdown();
-IMGUI_IMPL_API void     ImGui_ImplX11_NewFrame(void* window);
+IMGUI_IMPL_API void     ImGui_ImplX11_NewFrame();
 
 // Handler for Win32 messages, update mouse/keyboard data.
 // You may or not need this for your implementation, but it can serve as reference for handling inputs.

overlay_experimental/linux/X11_Hook.cpp

@@ -41,14 +41,14 @@ void X11_Hook::prepareForOverlay(Display *display, Window wnd)
 {
     if (!initialized)
     {
-        ImGui_ImplX11_Init(display);
+        ImGui_ImplX11_Init(display, (void*)wnd);
 
         game_wnd = wnd;
 
         initialized = true;
     }
 
-    ImGui_ImplX11_NewFrame((void*)wnd);
+    ImGui_ImplX11_NewFrame();
 }
 
 /////////////////////////////////////////////////////////////////////////////////////
@@ -68,6 +68,65 @@ bool IgnoreEvent(XEvent &event)
     return false;
 }
 
+int X11_Hook::check_for_overlay(Display *d, int num_events)
+{
+    static Time prev_time = {};
+
+    X11_Hook* inst = Inst();
+
+    if( inst->initialized )
+    {
+        XEvent event;
+        while(num_events)
+        {
+            //inst->_XPeekEvent(d, &event);
+            XPeekEvent(d, &event);
+
+            Steam_Overlay* overlay = get_steam_client()->steam_overlay;
+            bool show = overlay->ShowOverlay();
+            // Is the event is a key press
+            if (event.type == KeyPress)
+            {
+                // Tab is pressed and was not pressed before
+                //if (event.xkey.keycode == inst->_XKeysymToKeycode(d, XK_Tab) && event.xkey.state & ShiftMask)
+                if (event.xkey.keycode == XKeysymToKeycode(d, XK_Tab) && event.xkey.state & ShiftMask)
+                {
+                    // if key TAB is held, don't make the overlay flicker :p
+                    if( event.xkey.time != prev_time)
+                    {
+                        overlay->ShowOverlay(!overlay->ShowOverlay());
+
+                        if (overlay->ShowOverlay())
+                            show = true;
+                    }
+                }
+            }
+            //else if(event.type == KeyRelease && event.xkey.keycode == inst->_XKeysymToKeycode(d, XK_Tab))
+            else if(event.type == KeyRelease && event.xkey.keycode == XKeysymToKeycode(d, XK_Tab))
+            {
+                prev_time = event.xkey.time;
+            }
+
+            if (show)
+            {
+                ImGui_ImplX11_EventHandler(event);
+
+                if (IgnoreEvent(event))
+                {
+                    //inst->_XNextEvent(d, &event);
+                    XNextEvent(d, &event);
+                    --num_events;
+                }
+                else
+                    break;
+            }
+            else
+                break;
+        }
+    }
+    return num_events;
+}
+
 int X11_Hook::MyXEventsQueued(Display *display, int mode)
 {
     X11_Hook* inst = X11_Hook::Inst();
@@ -76,53 +135,9 @@ int X11_Hook::MyXEventsQueued(Display *display, int mode)
 
     if( res )
     {
-        static Time prev_time = {};
+        res = inst->check_for_overlay(display, res);
-
-        XEvent event;
-        //inst->_XPeekEvent(display, &event);
-        XPeekEvent(display, &event);
-
-        Steam_Overlay* overlay = get_steam_client()->steam_overlay;
-        bool show = overlay->ShowOverlay();
-        // Is the event is a key press
-        if (event.type == KeyPress)
-        {
-            // Tab is pressed and was not pressed before
-            //if (event.xkey.keycode == inst->_XKeysymToKeycode(display, XK_Tab) && event.xkey.state & ShiftMask)
-            if (event.xkey.keycode == XKeysymToKeycode(display, XK_Tab) && event.xkey.state & ShiftMask)
-            {
-                // if key TAB is held, don't make the overlay flicker :p
-                if( event.xkey.time != prev_time)
-                {
-                    overlay->ShowOverlay(!overlay->ShowOverlay());
-
-                    if (overlay->ShowOverlay())
-                        show = true;
-                }
-            }
-        }
-        //else if(event.type == KeyRelease && event.xkey.keycode == inst->_XKeysymToKeycode(display, XK_Tab))
-        else if(event.type == KeyRelease && event.xkey.keycode == XKeysymToKeycode(display, XK_Tab))
-        {
-            prev_time = event.xkey.time;
-        }
-
-        if (show)
-        {
-            ImGui_ImplX11_EventHandler(event);
-
-            if (IgnoreEvent(event))
-            {
-                //inst->_XNextEvent(display, &event);
-                XNextEvent(display, &event);
-                return 0;
-            }
-        }
     }
 
-    // XEventsQueued returns the num of events available.
-    // Usually, games tend to read all events queued before calling again XEventsQueued
-    // making us unavailable to intercept undesired events
     return res;
 }
 
@@ -140,19 +155,9 @@ int X11_Hook::MyXPending(Display* display)
 {
     int res = Inst()->_XPending(display);
 
-    if( res && get_steam_client()->steam_overlay->ShowOverlay() )
+    if( res )
     {
-        XEvent event;
+        res = Inst()->check_for_overlay(display, res);
-        //Inst()->_XPeekEvent(display, &event);
-        XPeekEvent(display, &event);
-        if( IgnoreEvent(event) )
-        {
-            ImGui_ImplX11_EventHandler(event);
-
-            //Inst()->_XNextEvent(display, &event);
-            XNextEvent(display, &event);
-            res = 0;
-        }
     }
 
     return res;

overlay_experimental/linux/X11_Hook.h

@@ -24,6 +24,7 @@ private:
 
     // Functions
     X11_Hook();
+    int check_for_overlay(Display *d, int num_events);
 
     // Hook to X11 window messages