feat: add more debug tools to gui

src/cpu.rs

@@ -73,15 +73,12 @@ impl Cpu {
     ///
     /// If opcode == 0xCB, then decoding costs 4 cycles.
     /// Otherwise, decoding is free
-    pub(crate) fn decode(&mut self, mut opcode: u8) -> Instruction {
+    pub(crate) fn decode(&mut self, opcode: u8) -> Instruction {
-        let instr = if opcode == 0xCB {
+        if opcode == 0xCB {
-            opcode = self.fetch();
+            Instruction::decode(self.fetch(), true)
-            Instruction::decode(opcode, true)
         } else {
             Instruction::decode(opcode, false)
-        };
+        }
-
-        instr.unwrap_or_else(|| panic!("{:#04X} is an invalid instruction", opcode))
     }
 
     /// Execute an [Instruction].
@@ -366,15 +363,12 @@ impl Cpu {
     }
 
     fn _dbg_instr(&self) -> Instruction {
-        let mut byte = self.read_byte(self.reg.pc);
+        let byte = self.read_byte(self.reg.pc);
-        let instr = if byte == 0xCB {
+        if byte == 0xCB {
-            byte = self.read_byte(self.reg.pc + 1);
+            Instruction::decode(self.read_byte(self.reg.pc + 1), true)
-            Instruction::decode(byte, true)
         } else {
             Instruction::decode(byte, false)
-        };
+        }
-
-        instr.unwrap_or_else(|| panic!("{:#04X} is an invalid instruction", byte))
     }
 }
 

src/emu.rs

@@ -18,7 +18,13 @@ pub const CYCLES_IN_FRAME: Cycle = 456 * 154; // 456 Cycles times 154 scanlines
 pub(crate) const SM83_CLOCK_SPEED: u64 = 0x40_0000; // Hz which is 4.194304Mhz
 const DEFAULT_TITLE: &str = "Game Boy Screen";
 
-pub fn run_frame(cpu: &mut Cpu, gamepad: &mut Gilrs, key: KeyboardInput) -> Cycle {
+#[inline]
+pub fn run_frame(cpu: &mut Cpu, gamepad: &mut Gilrs, key: KeyboardInput) {
+    run(cpu, gamepad, key, CYCLES_IN_FRAME)
+}
+
+#[inline]
+pub fn run(cpu: &mut Cpu, gamepad: &mut Gilrs, key: KeyboardInput, cycles: Cycle) {
     let mut elapsed = 0;
 
     if let Some(event) = gamepad.next_event() {
@@ -26,11 +32,9 @@ pub fn run_frame(cpu: &mut Cpu, gamepad: &mut Gilrs, key: KeyboardInput) -> Cycl
     }
     crate::joypad::handle_keyboard_input(&mut cpu.bus.joyp, key);
 
-    while elapsed < CYCLES_IN_FRAME {
+    while elapsed < cycles {
         elapsed += cpu.step();
     }
-
-    elapsed
 }
 
 pub fn save_and_exit(cpu: &Cpu, control_flow: &mut ControlFlow) {

src/gui.rs

@@ -26,6 +26,7 @@ pub struct GuiState {
     /// When true, egui winit should exit the application
     pub quit: bool,
     pub title: String,
+    pub mode: EmuMode,
 }
 
 impl GuiState {
@@ -33,10 +34,19 @@ impl GuiState {
         Self {
             title,
             quit: Default::default(),
+            mode: EmuMode::Running,
         }
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum EmuMode {
+    Running,
+    StepFrame,
+    Stopped,
+    Step,
+}
+
 /// To avoid using an [Option<KeyboardInput>] to keep track of user input from winit,
 /// we can use a "default" value. However, in order for this to work the chosen "default"
 /// value must be an **unused** key, so that it is ignored by the emulator.
@@ -223,7 +233,7 @@ pub fn execute_render_pass(
 
 #[inline]
 pub fn draw_egui(cpu: &Cpu, app: &mut GuiState, ctx: &CtxRef, texture_id: TextureId) {
-    use crate::{cpu, instruction};
+    use crate::{cpu, instruction, ppu};
 
     fn selectable_text(ui: &mut egui::Ui, mut text: &str) -> egui::Response {
         ui.add(egui::TextEdit::multiline(&mut text).code_editor())
@@ -247,6 +257,17 @@ pub fn draw_egui(cpu: &Cpu, app: &mut GuiState, ctx: &CtxRef, texture_id: Textur
             selectable_text(ui, &instruction::dbg::tmp_disasm(cpu, 20));
         });
 
+        egui::Window::new("Settings").show(ctx, |ui| {
+            egui::ComboBox::from_label("Emulation Mode")
+                .selected_text(format!("{:?}", app.mode))
+                .show_ui(ui, |ui| {
+                    ui.selectable_value(&mut app.mode, EmuMode::Running, "Running");
+                    ui.selectable_value(&mut app.mode, EmuMode::Stopped, "Stopped");
+                    ui.selectable_value(&mut app.mode, EmuMode::StepFrame, "Step Frame");
+                    ui.selectable_value(&mut app.mode, EmuMode::Step, "Step");
+                })
+        });
+
         egui::Window::new("GB Info").show(ctx, |ui| {
             ui.horizontal(|ui| {
                 ui.vertical(|ui| {
@@ -262,10 +283,21 @@ pub fn draw_egui(cpu: &Cpu, app: &mut GuiState, ctx: &CtxRef, texture_id: Textur
                 });
 
                 ui.vertical(|ui| {
+                    let ppu = &cpu.bus.ppu;
+
                     ui.heading("PPU");
 
-                    ui.monospace("LY: ?");
+                    ui.monospace(format!("LY: {}", ppu::dbg::ly(ppu)));
-                    ui.monospace("SCX: ?");
+                    ui.horizontal(|ui| {
+                        ui.monospace(format!("SCX: {}", ppu::dbg::scx(ppu)));
+                        ui.monospace(format!("SCY: {}", ppu::dbg::scy(ppu)));
+                    });
+                    ui.horizontal(|ui| {
+                        ui.monospace(format!("WX: {}", ppu::dbg::wx(ppu)));
+                        ui.monospace(format!("WY: {}", ppu::dbg::wy(ppu)));
+                    });
+
+                    ui.monospace(format!("Mode: {:?}", ppu::dbg::mode(ppu)))
                 });
             });
 
@@ -312,3 +344,12 @@ pub fn draw_egui(cpu: &Cpu, app: &mut GuiState, ctx: &CtxRef, texture_id: Textur
         })
     });
 }
+
+pub mod kbd {
+    use winit::event::{ElementState, KeyboardInput, VirtualKeyCode};
+
+    pub fn space_released(input: &KeyboardInput) -> bool {
+        let keycode = input.virtual_keycode;
+        matches!(input.state, ElementState::Released if keycode == Some(VirtualKeyCode::Space))
+    }
+}

src/instruction.rs

@@ -58,6 +58,7 @@ pub(crate) enum Instruction {
     BIT(u8, Register),
     RES(u8, Register),
     SET(u8, Register),
+    Invalid,
 }
 
 impl std::fmt::Debug for Instruction {
@@ -109,6 +110,7 @@ impl std::fmt::Debug for Instruction {
             BIT(b, r) => write!(f, "BIT {}, {:?}", b, r),
             RES(b, r) => write!(f, "RES {}, {:?}", b, r),
             SET(b, r) => write!(f, "SET {}, {:?}", b, r),
+            Invalid => f.write_str("???"),
         }
     }
 }
@@ -1294,6 +1296,7 @@ impl Instruction {
                     }
                 }
             }
+            Instruction::Invalid => panic!("Attempted to execute invalid instruction"),
         }
     }
 
@@ -1538,7 +1541,7 @@ impl Instruction {
 }
 
 impl Instruction {
-    pub(crate) fn decode(byte: u8, prefixed: bool) -> Option<Self> {
+    pub(crate) fn decode(byte: u8, prefixed: bool) -> Self {
         if prefixed {
             Self::prefixed(byte)
         } else {
@@ -1546,139 +1549,132 @@ impl Instruction {
         }
     }
 
-    fn unprefixed(byte: u8) -> Option<Self> {
+    fn unprefixed(byte: u8) -> Self {
         use Instruction::*;
 
         match byte {
             // NOP
-            0o000 => Some(NOP),
+            0o000 => NOP,
             // LD (u16), SP
-            0o010 => Some(LD(LDTarget::IndirectImmediateWord, LDSource::SP)),
+            0o010 => LD(LDTarget::IndirectImmediateWord, LDSource::SP),
             // STOP
-            0o020 => Some(STOP),
+            0o020 => STOP,
             // JR i8
-            0o030 => Some(JR(JpCond::Always)),
+            0o030 => JR(JpCond::Always),
             // JR cond i8
-            0o040 | 0o050 | 0o060 | 0o070 => Some(JR(jump_cond((byte >> 3) & 0x03))),
+            0o040 | 0o050 | 0o060 | 0o070 => JR(jump_cond((byte >> 3) & 0x03)),
             // LD r16, u16
-            0o001 | 0o021 | 0o041 | 0o061 => Some(LD(
+            0o001 | 0o021 | 0o041 | 0o061 => LD(
                 LDTarget::Group1(group1((byte >> 4) & 0x03)),
                 LDSource::ImmediateWord,
-            )),
+            ),
             // ADD HL, r16
-            0o011 | 0o031 | 0o051 | 0o071 => Some(ADD(
+            0o011 | 0o031 | 0o051 | 0o071 => {
-                AddTarget::HL,
+                ADD(AddTarget::HL, AddSource::Group1(group1((byte >> 4) & 0x03)))
-                AddSource::Group1(group1((byte >> 4) & 0x03)),
+            }
-            )),
             // LD (r16), A
-            0o002 | 0o022 | 0o042 | 0o062 => Some(LD(
+            0o002 | 0o022 | 0o042 | 0o062 => LD(
                 LDTarget::IndirectGroup2(group2((byte >> 4) & 0x03)),
                 LDSource::A,
-            )),
+            ),
             // LD A, (r16)
-            0o012 | 0o032 | 0o052 | 0o072 => Some(LD(
+            0o012 | 0o032 | 0o052 | 0o072 => LD(
                 LDTarget::A,
                 LDSource::IndirectGroup2(group2((byte >> 4) & 0x03)),
-            )),
+            ),
             // INC r16
-            0o003 | 0o023 | 0o043 | 0o063 => {
+            0o003 | 0o023 | 0o043 | 0o063 => INC(AllRegisters::Group1(group1((byte >> 4) & 0x03))),
-                Some(INC(AllRegisters::Group1(group1((byte >> 4) & 0x03))))
-            }
             // DEC r16
-            0o013 | 0o033 | 0o053 | 0o073 => {
+            0o013 | 0o033 | 0o053 | 0o073 => DEC(AllRegisters::Group1(group1((byte >> 4) & 0x03))),
-                Some(DEC(AllRegisters::Group1(group1((byte >> 4) & 0x03))))
-            }
             // INC r8
             0o004 | 0o014 | 0o024 | 0o034 | 0o044 | 0o054 | 0o064 | 0o074 => {
-                Some(INC(AllRegisters::Register(register((byte >> 3) & 0x07))))
+                INC(AllRegisters::Register(register((byte >> 3) & 0x07)))
             }
             // DEC r8
             0o005 | 0o015 | 0o025 | 0o035 | 0o045 | 0o055 | 0o065 | 0o075 => {
-                Some(DEC(AllRegisters::Register(register((byte >> 3) & 0x07))))
+                DEC(AllRegisters::Register(register((byte >> 3) & 0x07)))
             }
             // LD r8, u8
-            0o006 | 0o016 | 0o026 | 0o036 | 0o046 | 0o056 | 0o066 | 0o076 => Some(LD(
+            0o006 | 0o016 | 0o026 | 0o036 | 0o046 | 0o056 | 0o066 | 0o076 => LD(
                 LDTarget::Register(register((byte >> 3) & 0x07)),
                 LDSource::ImmediateByte,
-            )),
+            ),
             // RLCA, RRCA, RLA, RRA, DAA, CPL, SCF, and CCF
             0o007 | 0o017 | 0o027 | 0o037 | 0o047 | 0o057 | 0o067 | 0o077 => {
-                Some(flag_instr((byte >> 3) & 0x07))
+                flag_instr((byte >> 3) & 0x07)
             }
             // HALT
-            0o166 => Some(HALT),
+            0o166 => HALT,
             // LD r8, r8
-            0o100..=0o177 => Some(LD(
+            0o100..=0o177 => LD(
                 LDTarget::Register(register((byte >> 3) & 0x07)),
                 LDSource::Register(register(byte & 0x07)),
-            )),
+            ),
             // ADD, ADC, SUB, SBC, AND, XOR, OR, and CP
-            0o200..=0o277 => Some(alu_reg_instr((byte >> 3) & 0x07, byte & 0x07)),
+            0o200..=0o277 => alu_reg_instr((byte >> 3) & 0x07, byte & 0x07),
             // RET cond
-            0o300 | 0o310 | 0o320 | 0o330 => Some(RET(jump_cond((byte >> 3) & 0x03))),
+            0o300 | 0o310 | 0o320 | 0o330 => RET(jump_cond((byte >> 3) & 0x03)),
             // LD (0xFF00 + u8), A
-            0o340 => Some(LD(LDTarget::IoWithImmediateOffset, LDSource::A)),
+            0o340 => LD(LDTarget::IoWithImmediateOffset, LDSource::A),
             // ADD SP, i8
-            0o350 => Some(ADD(AddTarget::SP, AddSource::ImmediateSignedByte)),
+            0o350 => ADD(AddTarget::SP, AddSource::ImmediateSignedByte),
             // LD A, (0xFF00 + u8)
-            0o360 => Some(LD(LDTarget::A, LDSource::IoWithImmediateOffset)),
+            0o360 => LD(LDTarget::A, LDSource::IoWithImmediateOffset),
             // LD HL, SP + i8
-            0o370 => Some(LDHL),
+            0o370 => LDHL,
             // POP r16
-            0o301 | 0o321 | 0o341 | 0o361 => Some(POP(group3((byte >> 4) & 0x03))),
+            0o301 | 0o321 | 0o341 | 0o361 => POP(group3((byte >> 4) & 0x03)),
             // RET
-            0o311 => Some(RET(JpCond::Always)),
+            0o311 => RET(JpCond::Always),
             // RETI
-            0o331 => Some(RETI),
+            0o331 => RETI,
             // JP HL
-            0o351 => Some(JP(JpCond::Always, JpLoc::HL)),
+            0o351 => JP(JpCond::Always, JpLoc::HL),
             // LD SP, HL
-            0o371 => Some(LD(LDTarget::SP, LDSource::HL)),
+            0o371 => LD(LDTarget::SP, LDSource::HL),
             // JP cond u16
             0o302 | 0o312 | 0o322 | 0o332 => {
-                Some(JP(jump_cond((byte >> 3) & 0x03), JpLoc::ImmediateWord))
+                JP(jump_cond((byte >> 3) & 0x03), JpLoc::ImmediateWord)
             }
             // LD (0xFF00 + C), A
-            0o342 => Some(LD(LDTarget::IoWithC, LDSource::A)),
+            0o342 => LD(LDTarget::IoWithC, LDSource::A),
             // LD (u16), A
-            0o352 => Some(LD(LDTarget::IndirectImmediateWord, LDSource::A)),
+            0o352 => LD(LDTarget::IndirectImmediateWord, LDSource::A),
             // LD A, (0xFF00 + C)
-            0o362 => Some(LD(LDTarget::A, LDSource::IoWithC)),
+            0o362 => LD(LDTarget::A, LDSource::IoWithC),
             // LD A, (u16)
-            0o372 => Some(LD(LDTarget::A, LDSource::IndirectImmediateWord)),
+            0o372 => LD(LDTarget::A, LDSource::IndirectImmediateWord),
             // JP u16
-            0o303 => Some(JP(JpCond::Always, JpLoc::ImmediateWord)),
+            0o303 => JP(JpCond::Always, JpLoc::ImmediateWord),
             // DI
-            0o363 => Some(DI),
+            0o363 => DI,
             // EI
-            0o373 => Some(EI),
+            0o373 => EI,
             // CALL cond u16
-            0o304 | 0o314 | 0o324 | 0o334 => Some(CALL(jump_cond((byte >> 3) & 0x03))),
+            0o304 | 0o314 | 0o324 | 0o334 => CALL(jump_cond((byte >> 3) & 0x03)),
             // PUSH r16
-            0o305 | 0o325 | 0o345 | 0o365 => Some(PUSH(group3((byte >> 4) & 0x03))),
+            0o305 | 0o325 | 0o345 | 0o365 => PUSH(group3((byte >> 4) & 0x03)),
-            0o315 => Some(CALL(JpCond::Always)),
+            0o315 => CALL(JpCond::Always),
             0o306 | 0o316 | 0o326 | 0o336 | 0o346 | 0o356 | 0o366 | 0o376 => {
-                Some(alu_imm_instr((byte >> 3) & 0x07))
+                alu_imm_instr((byte >> 3) & 0x07)
             }
-            0o307 | 0o317 | 0o327 | 0o337 | 0o347 | 0o357 | 0o367 | 0o377 => {
+            0o307 | 0o317 | 0o327 | 0o337 | 0o347 | 0o357 | 0o367 | 0o377 => RST(byte & 0b00111000),
-                Some(RST(byte & 0b00111000))
+            _ => Invalid, // 0xCB is 0o313
-            }
-            _ => None, // 0xCB is 0o313
         }
     }
 
-    fn prefixed(byte: u8) -> Option<Self> {
+    fn prefixed(byte: u8) -> Self {
         use Instruction::*;
 
         match byte {
             // RLC, RRC, RL, RR, SLA, SRA, SWAP and SRL
-            0o000..=0o077 => Some(prefix_alu((byte >> 3) & 0x07, byte & 0x07)),
+            0o000..=0o077 => prefix_alu((byte >> 3) & 0x07, byte & 0x07),
             // BIT bit, r8
-            0o100..=0o177 => Some(BIT((byte >> 3) & 0x07, register(byte & 0x07))),
+            0o100..=0o177 => BIT((byte >> 3) & 0x07, register(byte & 0x07)),
             // RES bit, r8
-            0o200..=0o277 => Some(RES((byte >> 3) & 0x07, register(byte & 0x07))),
+            0o200..=0o277 => RES((byte >> 3) & 0x07, register(byte & 0x07)),
             // SET bit, r8
-            0o300..=0o377 => Some(SET((byte >> 3) & 0x07, register(byte & 0x07))),
+            0o300..=0o377 => SET((byte >> 3) & 0x07, register(byte & 0x07)),
         }
     }
 }
@@ -2163,7 +2159,7 @@ pub(crate) mod dbg {
     use super::{AllRegisters, BusIo, Cpu, Instruction, RegisterPair};
 
     pub(crate) fn tmp_disasm(cpu: &Cpu, limit: u8) -> String {
-        let mut asm = String::new();
+        let mut sm83_asm = String::new();
         let mut pc = cpu.register_pair(RegisterPair::PC);
 
         for _ in 0..limit {
@@ -2179,15 +2175,17 @@ pub(crate) mod dbg {
                 Instruction::unprefixed(opcode)
             };
 
-            if let Some(instr) = maybe_instr {
+            match maybe_instr {
-                let instr_asm = format!("{:04X} {:?}\n", pc - 1, instr);
+                Instruction::Invalid => {}
-                asm.push_str(&instr_asm);
+                instr => {
-
+                    let asm = format!("{:04X} {:?}\n", pc - 1, instr);
+                    sm83_asm.push_str(&asm);
                     pc += delta::pc_inc_count(instr)
                 }
             }
+        }
 
-        asm
+        sm83_asm
     }
 
     fn disasm(cpu: &Cpu, pc: u16, instr: Instruction) -> String {

src/lib.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::derivable_impls)] // Will remove this if bitfield-rs allows default impls
+
 pub use apu::gen::init as spsc_init;
 pub type Cycle = u64;
 

src/main.rs

@@ -2,6 +2,7 @@ use std::time::Instant;
 
 use clap::{crate_authors, crate_description, crate_name, crate_version, App, Arg};
 use egui_wgpu_backend::RenderPass;
+use gb::gui::EmuMode;
 use gb::{emu, gui};
 use gilrs::Gilrs;
 use gui::GuiState;
@@ -129,7 +130,19 @@ fn main() {
                     emu::save_and_exit(&cpu, control_flow);
                 }
 
-                emu::run_frame(&mut cpu, &mut gamepad, last_key);
+                match app.mode {
+                    EmuMode::Running => emu::run_frame(&mut cpu, &mut gamepad, last_key),
+                    EmuMode::StepFrame if gui::kbd::space_released(&last_key) => {
+                        emu::run_frame(&mut cpu, &mut gamepad, last_key)
+                    }
+                    EmuMode::Step if gui::kbd::space_released(&last_key) => {
+                        emu::run(&mut cpu, &mut gamepad, last_key, 4);
+                    }
+                    _ => {}
+                };
+
+                // Input has been consumed, reset it
+                last_key = gui::unused_key();
 
                 window.request_redraw();
             }

src/ppu.rs

@@ -910,3 +910,31 @@ struct WindowStatus {
     /// drawing from the window tile map is true
     enabled: bool,
 }
+
+pub(crate) mod dbg {
+    use super::{Ppu, PpuMode};
+
+    pub(crate) fn ly(ppu: &Ppu) -> u8 {
+        ppu.pos.line_y
+    }
+
+    pub(crate) fn scx(ppu: &Ppu) -> u8 {
+        ppu.pos.scroll_x
+    }
+
+    pub(crate) fn scy(ppu: &Ppu) -> u8 {
+        ppu.pos.scroll_y
+    }
+
+    pub(crate) fn mode(ppu: &Ppu) -> PpuMode {
+        ppu.stat.mode()
+    }
+
+    pub(crate) fn wx(ppu: &Ppu) -> i16 {
+        ppu.pos.window_x as i16
+    }
+
+    pub(crate) fn wy(ppu: &Ppu) -> i16 {
+        ppu.pos.window_y as i16
+    }
+}