feat(ui): implement pausing

lib/zba-util

@@ -1 +1 @@
-Subproject commit c1388c731820d9847c9d54f698c55e07752bc5ea
+Subproject commit 72349459ec29ee2d910a3dd3274be00254a7acd4

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

@@ -119,7 +119,7 @@ pub fn main() void {
         const thread = std.Thread.spawn(.{}, Server.run, .{ &server, allocator, &quit }) catch |e| exitln("gdb server thread crashed: {}", .{e});
         defer thread.join();
 
-        gui.run(.{
+        gui.run(.Debug, .{
             .cpu = &cpu,
             .scheduler = &scheduler,
             .channel = &channel,
@@ -127,10 +127,14 @@ 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();
 
-        gui.run(.{
+        gui.run(.Standard, .{
             .cpu = &cpu,
             .scheduler = &scheduler,
             .channel = &channel,

src/platform.zig

@@ -99,7 +99,9 @@ pub const Gui = struct {
         scheduler: *Scheduler,
     };
 
-    pub fn run(self: *Self, opt: RunOptions) !void {
+    const RunMode = enum { Standard, Debug };
+
+    pub fn run(self: *Self, comptime mode: RunMode, opt: RunOptions) !void {
         const cpu = opt.cpu;
         const tracker = opt.tracker;
         const channel = opt.channel;
@@ -121,13 +123,6 @@ 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;
@@ -190,15 +185,46 @@ pub const Gui = struct {
                 }
             }
 
-            {
-                channel.emu.push(.Pause);
-                defer channel.emu.push(.Resume);
+            zgui.backend.newFrame(@intToFloat(f32, win_dim.width), @intToFloat(f32, win_dim.height));
 
-                // 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}),
+            switch (self.state.emulation) {
+                .Transition => |inner| switch (inner) {
+                    .Active => {
+                        _ = channel.gui.pop();
+
+                        channel.emu.push(.Resume);
+                        self.state.emulation = .Active;
+                    },
+                    .Inactive => {
+                        // Assert that double pausing is impossible
+                        if (channel.gui.peek()) |value|
+                            std.debug.assert(value != .Paused);
+
+                        channel.emu.push(.Pause);
+                        self.state.emulation = .Inactive;
+                    },
+                },
+                .Active => {
+                    const is_std = mode == .Standard;
+
+                    if (is_std) channel.emu.push(.Pause);
+                    defer if (is_std) channel.emu.push(.Resume);
+
+                    switch (mode) {
+                        .Standard => {
+                            // TODO: add timeout
+                            while (true) switch (channel.gui.pop() orelse continue) {
+                                .Paused => break,
+                                .Quit => unreachable, // only signaled in debug mode
                             };
+                        },
+                        .Debug => blk: {
+                            switch (channel.gui.pop() orelse break :blk) {
+                                .Paused => unreachable, // only in standard mode
+                                .Quit => break :emu_loop, // FIXME: gdb side of emu is seriously out-of-date...
+                            }
+                        },
+                    }
 
                     // Add FPS count to the histogram
                     if (tracker) |t| self.state.fps_hist.push(t.value()) catch {};
@@ -213,16 +239,18 @@ pub const Gui = struct {
                         opengl_impl.drawScreenTexture(emu_tex, prog_id, objects, buf);
                     }
 
+                    imgui.draw(&self.state, out_tex, cpu);
+                },
+                .Inactive => imgui.draw(&self.state, out_tex, cpu),
+            }
+
             // Background Colour
             const size = zgui.io.getDisplaySize();
             gl.viewport(0, 0, @floatToInt(GLsizei, size[0]), @floatToInt(GLsizei, size[1]));
             gl.clearColor(0, 0, 0, 1.0);
             gl.clear(gl.COLOR_BUFFER_BIT);
 
-                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);
         }