From db5ab5f63c5a255c130d0bd773ce0fc72becaffa Mon Sep 17 00:00:00 2001
From: joevt <joevt@shaw.ca>
Date: Sun, 9 Aug 2026 04:35:46 -0700
Subject: [PATCH] display_sdl: Make auto grab mouse optional.

Add a command line option to enable auto grab.
Default to the previous behavior before the auto grab feature was added.

Add a debugger command to enable or disable auto grab.

Notes:
Auto grab mouse currently only works for graphics controllers and guest
OSs that use a hardware cursor and only if the emulation sets
cursor_dirty to true (i.e. not emulation that uses cursor_ovl_cb).
---
 debugger/debugger.cpp         | 16 ++++++++++++++++
 devices/video/display_sdl.cpp |  8 +++++++-
 main.cpp                      |  5 +++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/debugger/debugger.cpp b/debugger/debugger.cpp
index d2ccba19..39e0417b 100644
--- a/debugger/debugger.cpp
+++ b/debugger/debugger.cpp
@@ -58,6 +58,8 @@ using namespace std;
 #define COUT08X COUT0_X(8)
 #define COUT04X COUT0_X(4)
 
+extern bool g_auto_grab_mouse;
+
 static uint32_t str2addr(string& addr_str) {
     try {
         return static_cast<uint32_t>(stoul(addr_str, NULL, 0));
@@ -116,6 +118,8 @@ static void show_help() {
     cout << "  printenv       -- print current NVRAM settings." << endl;
     cout << "  setenv V N     -- set NVRAM variable V to value N." << endl;
     cout << endl;
+    cout << "  autograbmouse H -- auto grab the mouse if H is not zero." << endl;
+    cout << endl;
     cout << "  restart        -- restart the machine" << endl;
     cout << "  quit           -- quit the debugger" << endl;
     cout << endl;
@@ -1169,6 +1173,18 @@ void DppcDebugger::enter_debugger() {
                 via_obj->assert_int(irq_bit);
             });
 #endif
+        } else if (cmd == "autograbmouse") {
+            cmd = "";
+            string value;
+            int num;
+            ss >> value;
+            try {
+                num = str2num(value);
+            } catch (invalid_argument& exc) {
+                cout << exc.what() << endl;
+                continue;
+            }
+            g_auto_grab_mouse = num;
         } else {
             if (!cmd.empty()) {
                 cout << "Unknown command: " << cmd << endl;
diff --git a/devices/video/display_sdl.cpp b/devices/video/display_sdl.cpp
index 486ca4ef..e983a864 100644
--- a/devices/video/display_sdl.cpp
+++ b/devices/video/display_sdl.cpp
@@ -26,6 +26,8 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 #include <cmath>
 #include <string>
 
+bool g_auto_grab_mouse = false;
+
 static const char * get_full_screen_mode_string(int scale_mode) {
 #define onemode(x) case Display::x: return #x ;
     switch(scale_mode) {
@@ -316,6 +318,7 @@ void Display::handle_events(const WindowEvent& wnd_event) {
         if (wnd_event.window_id == impl->disp_wnd_id) {
             SDL_SetHint(SDL_HINT_ALLOW_ALT_TAB_WHILE_GRABBED, "0");
             SDL_SetWindowKeyboardGrab(impl->display_wnd, SDL_TRUE);
+if (g_auto_grab_mouse) {
             // When the window (re)gains focus (e.g. the user clicks it), SDL
             // may have dropped the relative mouse grab on focus loss. Re-grab
             // it so the guest cursor keeps working; this is the reliable
@@ -324,6 +327,7 @@ void Display::handle_events(const WindowEvent& wnd_event) {
                 SDL_SetRelativeMouseMode(SDL_TRUE);
                 this->update_window_title();
             }
+}
         }
         break;
 
@@ -449,7 +453,7 @@ void Display::update_window_title()
         + " " + std::to_string(int(std::round(impl->renderer_scale_x * 100))) + "%";
     if (is_grabbed)
         new_window_title += " (Grabbed, Ctrl+G to release)";
-    else if (impl->guest_cursor_drawn)
+    else if (!g_auto_grab_mouse || impl->guest_cursor_drawn)
         new_window_title += " (Press Ctrl+G to grab)";
 
     if (new_window_title != old_window_title)
@@ -482,6 +486,7 @@ void Display::update(std::function<void(uint8_t *dst_buf, int dst_pitch)> conver
     SDL_RenderClear(impl->renderer);
     SDL_RenderCopy(impl->renderer, impl->disp_texture, NULL, &impl->dest_rect);
 
+if (g_auto_grab_mouse) {
     bool is_grabbed = SDL_GetRelativeMouseMode();
 
     // The guest draws its own cursor into the framebuffer (hardware cursor).
@@ -520,6 +525,7 @@ void Display::update(std::function<void(uint8_t *dst_buf, int dst_pitch)> conver
         impl->guest_cursor_drawn = draw_hw_cursor;
         this->update_window_title();
     }
+}
 
     // draw HW cursor if enabled
     if (draw_hw_cursor) {
diff --git a/main.cpp b/main.cpp
index 988ff301..ea862580 100644
--- a/main.cpp
+++ b/main.cpp
@@ -49,6 +49,8 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 #endif
 using namespace std;
 
+extern bool g_auto_grab_mouse;
+
 static void sigint_handler(int signum) {
     power_on = false;
     power_off_reason = po_signal_interrupt;
@@ -168,6 +170,9 @@ int main(int argc, char** argv) {
     CLI::Option* machine_opt = emu->add_option("-m,--machine",
         machine_str, "Specify machine ID");
 
+    emu->add_flag("--auto-grab-mouse", g_auto_grab_mouse,
+        "The guest cursor causes mouse to be grabbed");
+
     auto list_cmd = app.add_subcommand("list",
         "Display available machine configurations and exit");