From 4bd6c58aea6ee93ff6496ed7598c2163fee32b13 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Sat, 1 Jan 2022 12:10:55 +0100
Subject: [PATCH] uncapture

---
 app/src/screen.c | 39 +++++++++++++++++++++++++++++++++++++++
 app/src/screen.h |  3 +++
 2 files changed, 42 insertions(+)

diff --git a/app/src/screen.c b/app/src/screen.c
index 87c9830e..f615e545 100644
--- a/app/src/screen.c
+++ b/app/src/screen.c
@@ -366,6 +366,7 @@ screen_init(struct screen *screen, const struct screen_params *params) {
     screen->maximized = false;
     screen->event_failed = false;
     screen->mouse_captured = false;
+    screen->uncapture_key_pressed = 0;
 
     static const struct sc_video_buffer_callbacks cbs = {
         .on_new_frame = sc_video_buffer_on_new_frame,
@@ -753,6 +754,11 @@ screen_resize_to_pixel_perfect(struct screen *screen) {
                                             content_size.height);
 }
 
+static inline bool
+screen_is_uncapture_key(SDL_Keycode key) {
+    return key == SDLK_LALT || key == SDLK_LGUI || key == SDLK_RGUI;
+}
+
 bool
 screen_handle_event(struct screen *screen, SDL_Event *event) {
     switch (event->type) {
@@ -802,6 +808,39 @@ screen_handle_event(struct screen *screen, SDL_Event *event) {
                     break;
             }
             return true;
+        case SDL_KEYDOWN:
+            if (screen->im.mp->relative_mode && screen->mouse_captured) {
+                SDL_Keycode key = event->key.keysym.sym;
+                if (screen_is_uncapture_key(key)) {
+                    if (!screen->uncapture_key_pressed) {
+                        screen->uncapture_key_pressed = key;
+                        return true;
+                    } else {
+                        // Another uncapture key has been pressed, cancel mouse
+                        // uncapture
+                        screen->uncapture_key_pressed = 0;
+                        // Do not return, the event must be forwarded to the
+                        // input manager
+                    }
+                }
+            }
+            break;
+        case SDL_KEYUP:
+            if (screen->im.mp->relative_mode && screen->mouse_captured) {
+                SDL_Keycode key = event->key.keysym.sym;
+                SDL_Keycode uncapture_key_pressed =
+                    screen->uncapture_key_pressed;
+                screen->uncapture_key_pressed = 0;
+                if (key == uncapture_key_pressed) {
+                    // An uncapture key has been pressed then released:
+                    // uncapture the mouse
+                    screen_capture_mouse(screen, false);
+                    return true;
+                }
+                // Do not return, the event must be forwarded to the input
+                // manager
+            }
+            break;
         case SDL_MOUSEWHEEL:
         case SDL_MOUSEMOTION:
         case SDL_MOUSEBUTTONDOWN:
diff --git a/app/src/screen.h b/app/src/screen.h
index 9eb78fb7..ca32496f 100644
--- a/app/src/screen.h
+++ b/app/src/screen.h
@@ -52,6 +52,9 @@ struct screen {
     bool event_failed; // in case SDL_PushEvent() returned an error
 
     bool mouse_captured; // only relevant in relative mouse mode
+    // To disable mouse capture, an uncapture key (LALT, LGUI or RGUI) must be
+    // pressed. This variable tracks the pressed mod key.
+    SDL_Keycode uncapture_key_pressed;
 
     AVFrame *frame;
 };