feat(ui): implement pausing

src/imgui.zig

@@ -30,6 +30,7 @@ pub const State = struct {
 
     fps_hist: RingBuffer(u32),
     should_quit: bool = false,
+    emulation: Emulation,
 
     win_stat: WindowStatus = .{},
 
@@ -41,6 +42,12 @@ pub const State = struct {
         show_palette: bool = false,
     };
 
+    const Emulation = union(enum) {
+        Active,
+        Inactive,
+        Transition: enum { Active, Inactive },
+    };
+
     /// if zba is initialized with a ROM already provided, this initializer should be called
     /// with `title_opt` being non-null
     pub fn init(allocator: Allocator, title_opt: ?*const [12]u8) !@This() {
@@ -48,6 +55,7 @@ pub const State = struct {
 
         return .{
             .title = handleTitle(title_opt),
+            .emulation = if (title_opt == null) .Inactive else .Active,
             .fps_hist = RingBuffer(u32).init(history),
         };
     }
@@ -90,6 +98,7 @@ pub fn draw(state: *State, tex_id: GLuint, cpu: *Arm7tdmi) void {
                 };
 
                 state.title = handleTitle(&cpu.bus.pak.title);
+                state.emulation = .{ .Transition = .Active };
             }
         }
 
@@ -105,6 +114,14 @@ pub fn draw(state: *State, tex_id: GLuint, cpu: *Arm7tdmi) void {
             if (zgui.menuItem("Schedule", .{ .selected = state.win_stat.show_schedule }))
                 state.win_stat.show_schedule = true;
 
+            if (zgui.menuItem("Paused", .{ .selected = state.emulation == .Inactive })) {
+                state.emulation = switch (state.emulation) {
+                    .Active => .{ .Transition = .Inactive },
+                    .Inactive => .{ .Transition = .Active },
+                    else => state.emulation,
+                };
+            }
+
             if (zgui.menuItem("Restart", .{}))
                 emu.reset(cpu);
         }

src/main.zig

@@ -127,6 +127,10 @@ pub fn main() void {
     } else {
         var tracker = FpsTracker.init();
 
+        // emu should start paused if there's no ROM to run
+        if (paths.rom == null)
+            channel.emu.push(.Pause);
+
         const thread = std.Thread.spawn(.{}, emu.run, .{ &cpu, &scheduler, &tracker, &channel }) catch |e| exitln("emu thread panicked: {}", .{e});
         defer thread.join();
 

src/platform.zig

@@ -121,13 +121,6 @@ pub const Gui = struct {
         var win_dim: Dimensions = default_dim;
 
         emu_loop: while (true) {
-            // `quit` from RunOptions may be modified by the GDBSTUB thread,
-            // so we want to recognize that it may change to `true` and exit the GUI thread
-            if (channel.gui.pop()) |event| switch (event) {
-                .Quit => break :emu_loop,
-                .Paused => @panic("TODO: We want to peek (and then pop if it's .Quit), not always pop"),
-            };
-
             // Outside of `SDL.SDL_QUIT` below, the DearImgui UI might signal that the program
             // should exit, in which case we should also handle this
             if (self.state.should_quit) break :emu_loop;
@@ -190,14 +183,36 @@ pub const Gui = struct {
                 }
             }
 
-            {
+            switch (self.state.emulation) {
+                .Transition => |inner| switch (inner) {
+                    .Active => blk: {
+                        if (channel.gui.peek() == null) break :blk;
+                        if (channel.gui.peek().? != .Paused) break :blk;
+
+                        log.debug("-> Active | {?}", .{channel.gui.peek()});
+                        _ = channel.gui.pop();
+
+                        channel.emu.push(.Resume);
+                        self.state.emulation = .Active;
+                    },
+                    .Inactive => blk: {
+                        if (channel.gui.peek()) |value|
+                            if (value == .Paused) break :blk;
+
+                        log.debug("-> Inactive | {?}", .{channel.gui.peek()});
+
+                        channel.emu.push(.Pause);
+                        self.state.emulation = .Inactive;
+                    },
+                },
+                .Active => {
                     channel.emu.push(.Pause);
                     defer channel.emu.push(.Resume);
 
                     // Spin Loop until we know that the emu is paused
                     wait: while (true) switch (channel.gui.pop() orelse continue) {
                         .Paused => break :wait,
-                    else => |any| std.debug.panic("[Gui/Channel]: Unhandled Event: {}", .{any}),
+                        .Quit => break :emu_loop, // TODO: Ensure this behaves as expected
                     };
 
                     // Add FPS count to the histogram
@@ -212,6 +227,9 @@ pub const Gui = struct {
                         gl.viewport(0, 0, gba_width, gba_height);
                         opengl_impl.drawScreenTexture(emu_tex, prog_id, objects, buf);
                     }
+                },
+                .Inactive => {},
+            }
 
             // Background Colour
             const size = zgui.io.getDisplaySize();
@@ -222,7 +240,6 @@ pub const Gui = struct {
             zgui.backend.newFrame(@intToFloat(f32, win_dim.width), @intToFloat(f32, win_dim.height));
             imgui.draw(&self.state, out_tex, cpu);
             zgui.backend.draw();
-            }
 
             SDL.SDL_GL_SwapWindow(self.window);
         }