While SDL doesn't provide a direct way to disable mouse focus events, we can implement this behavior by filtering events and using window flags. Here's how to create windows that ignore mouse focus:
#include <SDL.h>
#include <iostream>
#include "Window.h"
class FocuslessWindow {
public:
FocuslessWindow() {
SDLWindow = SDL_CreateWindow(
"Focusless Window", 100, 100, 400, 300,
// Prevents focus stealing
SDL_WINDOW_MOUSE_CAPTURE
);
// Store the window ID for event filtering
WindowID = SDL_GetWindowID(SDLWindow);
}
~FocuslessWindow() {
if (SDLWindow) {
SDL_DestroyWindow(SDLWindow);
}
}
// Filter out focus events for this window
bool ShouldProcessEvent(const SDL_Event& E) {
if (E.type == SDL_WINDOWEVENT &&
E.window.windowID == WindowID
) {
switch (E.window.event) {
case SDL_WINDOWEVENT_ENTER:
case SDL_WINDOWEVENT_LEAVE:
case SDL_WINDOWEVENT_FOCUS_GAINED:
case SDL_WINDOWEVENT_FOCUS_LOST:
// Ignore these events
return false;
default:
break;
}
}
return true;
}
SDL_Window* SDLWindow{nullptr};
private:
Uint32 WindowID;
};
int main(int argc, char** argv) {
SDL_Init(SDL_INIT_VIDEO);
FocuslessWindow OverlayWindow;
// Regular window for comparison
Window NormalWindow;
SDL_Event E;
while (true) {
while (SDL_PollEvent(&E)) {
// Only process events for the regular window
if (E.type == SDL_WINDOWEVENT) {
if (E.window.windowID ==
SDL_GetWindowID(
NormalWindow.SDLWindow)) {
std::cout << "Normal window event\n";
} else if (OverlayWindow.
ShouldProcessEvent(E)) {
std::cout <<
"Filtered overlay window event\n";
}
}
}
NormalWindow.Update();
}
SDL_Quit();
return 0;
}Filtered overlay window event
Normal window event
Normal window eventThis is particularly useful for:
- Overlay windows that shouldn't interrupt gameplay
- Debug windows that display game state
- Toast notifications or status indicators
- UI elements that should stay visible without affecting focus
You can also create a reusable system for managing multiple windows with different focus behaviors:
#include <SDL.h>
#include <iostream>
#include <unordered_map>
#include <vector>
enum class FocusBehavior {
Normal,
Ignore,
AlwaysOnTop
};
class WindowManager {
public:
SDL_Window* CreateWindow(
const char* Title, int X, int Y,
int Width, int Height,
FocusBehavior Behavior
) {
Uint32 Flags{0};
if (Behavior == FocusBehavior::AlwaysOnTop) {
Flags |= SDL_WINDOW_ALWAYS_ON_TOP;
}
if (Behavior == FocusBehavior::Ignore) {
Flags |= SDL_WINDOW_MOUSE_CAPTURE;
}
SDL_Window* NewWindow{
SDL_CreateWindow(Title, X, Y, Width,
Height, Flags)};
if (NewWindow) {
Uint32 ID{SDL_GetWindowID(NewWindow)};
WindowBehaviors[ID] = Behavior;
Windows.push_back(NewWindow);
}
return NewWindow;
}
void HandleEvent(SDL_Event& E) {
if (E.type == SDL_WINDOWEVENT) {
auto It{
WindowBehaviors.find(
E.window.windowID)};
if (It != WindowBehaviors.end()) {
if (It->second == FocusBehavior::Ignore) {
// Drop focus events for ignored windows
switch (E.window.event) {
case SDL_WINDOWEVENT_ENTER:
case SDL_WINDOWEVENT_LEAVE:
return;
default:
break;
}
}
}
}
// Process the event normally
}
private:
std::vector<SDL_Window*> Windows;
std::unordered_map<Uint32, FocusBehavior>
WindowBehaviors;
};Remember that even if you ignore focus events, the window will still receive mouse input events. If you need to completely ignore mouse input, you'll need to filter those events as well.
Answers to questions are automatically generated and may not have been reviewed.
This Question is from the Lesson:
Managing Mouse Focus with SDL2
Learn how to track and respond to mouse focus events in SDL2, including handling multiple windows and customizing focus-related click behavior.
