Feature #19 - Adding graphical display. (closes #19) (#34)

* Most basic graphical library addition.

gpu.c and gpu.h use Allegro library to draw a black window with ROM
title as window title.
gpu.c has provisions for future additions of drawing logic.

Probably will be overhauled later, as it effectively ignores the V-Blank
interval.

* Special R/W (unfinished), proper gpu step and LCD STAT updating.

Palette memory to be found. It seems we lack information about CGB vs
DMG ROMs (Address 143). Scanline drawing logic still to be done.

GPU divided into GPU and DISPLAY, where DISPLAY handles the graphical
library. It should allow for easier change of graphical library, if need
arises.

* General cleanup. Future issues now separated more clearly.

Modes separated to an enum for clarity. Now int.h enum is prefixed by
module name to solve naming problems.

* Update build.yml

Include Allegro lib in build action.

* Code now uses stdbool.h instead of its own definition.

This allows for compatibility with other libraries.

* mzal's requested changes

static keyword added for module variables.
Includes and enums moved to .c if not needed in .h.
Unneeded functions removed.
Enums now explicitely numbered.
checking for window closing now called directly in main.
More complex defines now encapsulated.

* Second round of reviews implemented.

Fixed inconsistent spacing in display.c.
Recognised interrupts now named in request_interrupt().
main.c display_get_closed_status() call now uses shorter logic check.
Unneccessary comments in display.c removed.
Curly braces added to gpu.c elses when ifs use them.
Counter reset in GPU now uses -=_CYCLES_PER_SCANLINE.
Unneccessary white symbols removed from main.c

Co-authored-by: galeblon <32581949+galeblon@users.noreply.github.com>

.github/workflows/build.yml

@@ -8,6 +8,8 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+    - name: Install Allegro
+      run: sudo apt-get update && sudo apt-get install liballegro-acodec5-dev liballegro-audio5-dev liballegro-image5-dev liballegro-dialog5-dev liballegro-ttf5-dev liballegro-physfs5-dev
     - uses: actions/checkout@v2
     - name: make
       run: make

src/Makefile

@@ -1,7 +1,8 @@
 CC = gcc
 CFLAGS = -g -Wall -Wextra -pedantic -O0
 INCL = -I./include
-SRCS = cpu.c logger.c regs.c rom.c ints.c main.c mem.c debug.c
+SRCS = mem.c cpu.c logger.c regs.c rom.c ints.c gpu.c display.c main.c debug.c
+PKG = $$(pkg-config --libs allegro-5)
 OBJS = $(SRCS:.c=.o)
 BIN = gbc
 
@@ -11,7 +12,7 @@ gbc_debug: CFLAGS += -DDEBUG
 gbc_debug: gbc
 
 gbc: $(OBJS)
-	$(CC) $(CFLAGS) $(INCL) -o $(BIN) $(OBJS)
+	$(CC) $(CFLAGS) $(INCL) -o $(BIN) $(OBJS) $(PKG)
 
 .c.o:
 	$(CC) $(CFLAGS) $(INCL) -c $< -o $@

src/display.c

@@ -0,0 +1,121 @@
+#include<allegro5/allegro5.h>
+#include"cpu.h"
+#include"display.h"
+#include"logger.h"
+
+static ALLEGRO_DISPLAY     *g_display           = NULL;
+static ALLEGRO_TIMER       *g_timer             = NULL;
+static ALLEGRO_EVENT_QUEUE *g_close_event_queue = NULL;
+static ALLEGRO_EVENT_QUEUE *g_event_queue       = NULL;
+static ALLEGRO_EVENT       g_event;
+
+
+static void _display_error(enum logger_log_type type, char *title, char *message)
+{
+	char *full_message = logger_get_msg_buffer();
+	snprintf(
+		full_message,
+		LOG_MESSAGE_MAX_SIZE,
+		"[DISPLAY MODULE] %s\n",
+		message
+	);
+	logger_log(
+		type,
+		title,
+		full_message
+	);
+}
+
+void display_prepare(float frequency, char * rom_title)
+{
+	if(!al_init()) {
+		_display_error(
+			LOG_FATAL,
+			"ALLEGRO INIT",
+			"FAILED TO INITIALISE ALLEGRO."
+		);
+		return;
+	}
+
+	g_timer = al_create_timer(frequency);
+	if (!g_timer) {
+		_display_error(
+			LOG_FATAL,
+			"ALLEGRO TIMER",
+			"FAILED TO CREATE A TIMER."
+		);
+		return;
+	}
+
+	g_display = al_create_display( 160 * SCALING_FACTOR, 144 * SCALING_FACTOR );
+	if(!g_display) {
+		_display_error(
+			LOG_FATAL,
+			"ALLEGRO DISPLAY",
+			"FAILED TO INITIALISE DISPLAY."
+		);
+    	return;
+	}
+
+	g_event_queue = al_create_event_queue();
+	if (!g_event_queue) {
+		_display_error(
+			LOG_FATAL,
+			"ALLEGRO QUEUE",
+			"FAILED TO CREATE EVENT QUEUE."
+		);
+		return;
+	}
+
+	g_close_event_queue = al_create_event_queue();
+	if (!g_close_event_queue) {
+		_display_error(
+			LOG_FATAL,
+			"ALLEGRO QUEUE",
+			"FAILED TO CREATE EVENT QUEUE."
+		);
+		return;
+	}
+
+	al_register_event_source(
+		g_close_event_queue,
+		al_get_display_event_source(g_display)
+	);
+	al_register_event_source(
+		g_event_queue,
+		al_get_timer_event_source(g_timer)
+	);
+
+	al_start_timer(g_timer);
+
+	// Display a black screen, set the title
+	al_set_window_title(g_display, rom_title);
+	al_clear_to_color( al_map_rgb(0, 0, 0) );
+	al_flip_display();
+}
+
+
+bool display_get_closed_status(void)
+{
+	// Fetch the event (if one exists)
+	bool event_exists = al_get_next_event(g_close_event_queue, &g_event);
+
+	if(event_exists)
+		// Handle the event
+		switch (g_event.type) {
+			case ALLEGRO_EVENT_DISPLAY_CLOSE:
+				return true;
+			default:
+				return false;
+		}
+	else
+		return false;
+}
+
+
+void display_destroy(void)
+{
+	al_destroy_display(g_display);
+	al_destroy_event_queue(g_event_queue);
+	al_destroy_event_queue(g_close_event_queue);
+}