sdl2: add font rendering from a bitmap file

src/platform/sdl2.c

@@ -13,6 +13,31 @@
 static SDL_Window *w = NULL;
 static SDL_Renderer *r = NULL;
 
+/* Font surface */
+static SDL_Texture *font = NULL;
+
+/* Font configuration */
+
+#ifndef LARGE_FONT /* Small font */
+
+#define FONT_FILE    "font5x7.bmp"
+#define FONT_WIDTH   5
+#define FONT_HEIGHT  7
+#define FONT_OUTER   1
+#define FONT_INNER   2
+#define FONT_OFFSET  0
+
+#else /* Large font */
+
+#define FONT_FILE    "font10x12.bmp"
+#define FONT_WIDTH   10
+#define FONT_HEIGHT  12
+#define FONT_OUTER   3
+#define FONT_INNER   3
+#define FONT_OFFSET  32
+
+#endif /* Font size */
+
 //---
 //	Interface functions
 //---
@@ -42,8 +67,8 @@ void intf_line(int x1, int y1, int x2, int y2, int color)
 /* intf_size() - Get the dimensions of a string */
 void intf_size(char const *str, int *width, int *height)
 {
-	*width = 6 * strlen(str) - 1;
-	*height = 7;
+	*width = (FONT_WIDTH + 1) * strlen(str) - 1;
+	*height = FONT_HEIGHT;
 }
 
 /* intf_text() - Draw variable-width text */
@@ -54,9 +79,27 @@ void intf_text(char const *str, int x, int y, int color)
 	int B = color & 0xff;
 	SDL_SetRenderDrawColor(r, R, G, B, 255);
 
-	SDL_Rect rect = { .x = x, .y = y };
-	intf_size(str, &rect.w, &rect.h);
-	SDL_RenderDrawRect(r, &rect);
+	int c;
+	while((c = *str++))
+	{
+		int row = (c - FONT_OFFSET) >> 4;
+		int col = (c - FONT_OFFSET) & 15;
+
+		SDL_Rect src = {
+			.x = FONT_OUTER + (FONT_WIDTH + FONT_INNER) * col,
+			.y = FONT_OUTER + (FONT_HEIGHT + FONT_INNER) * row,
+			.w = FONT_WIDTH,
+			.h = FONT_HEIGHT,
+		};
+		SDL_Rect dst = { .x = x, .y = y, .w = src.w, .h = src.h };
+
+		SDL_RenderCopy(r, font, &src, &dst);
+		x += FONT_WIDTH + 1;
+	}
+
+//	SDL_Rect rect = { .x = x, .y = y };
+//	intf_size(str, &rect.w, &rect.h);
+//	SDL_RenderDrawRect(r, &rect);
 }
 
 //---
@@ -66,32 +109,30 @@ void intf_text(char const *str, int x, int y, int color)
 __attribute__((constructor))
 static void init(void)
 {
-	if(SDL_Init(SDL_INIT_VIDEO) < 0)
-	{
-		fprintf(stderr, "error: cannot initialize SDL backend: %s\n",
-			SDL_GetError());
-		exit(1);
+	#define fail(msg) { \
+		fprintf(stderr, "error: " msg ": %s\n", SDL_GetError()); \
+		exit(1); \
 	}
 
+	if(SDL_Init(SDL_INIT_VIDEO) < 0) fail("failed to initialize SDL");
+
 	int c = SDL_WINDOWPOS_CENTERED;
 	w = SDL_CreateWindow("2D rendering", c, c, 256, 128, 0);
-	if(!w)
-	{
-		fprintf(stderr, "error: cannot create SDL window: %s\n",
-			SDL_GetError());
-		exit(1);
-	}
+	if(!w) fail("cannot create SDL window");
 
 	r = SDL_CreateRenderer(w, -1, SDL_RENDERER_ACCELERATED);
-	if(!r)
-	{
-		fprintf(stderr, "error: cannot create SDL renderer: %s\n",
-			SDL_GetError());
-		exit(1);
-	}
+	if(!r) fail("cannot create SDL renderer");
 
 	SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "0");
 
+	/* Load the font */
+	SDL_Surface *font_surf = SDL_LoadBMP(FONT_FILE);
+	if(!font_surf) fail("cannot load font");
+
+	font = SDL_CreateTextureFromSurface(r, font_surf);
+	SDL_FreeSurface(font_surf);
+	if(!font) fail("cannot convert font to texture");
+
 	/* Make the window visible */
 	SDL_RenderPresent(r);
 
@@ -100,11 +141,15 @@ static void init(void)
 	TeX_intf_line(intf_line);
 	TeX_intf_size(intf_size);
 	TeX_intf_text(intf_text);
+
+	#undef fail
 }
 
 __attribute__((destructor))
 static void fini(void)
 {
+	if(font) SDL_DestroyTexture(font);
+	if(r) SDL_DestroyRenderer(r);
 	if(w) SDL_DestroyWindow(w);
 	SDL_Quit();
 }
@@ -115,7 +160,8 @@ static void fini(void)
 
 int main(void)
 {
-	char const * formula = "\\frac{x_7}{"
+	char const * formula =
+	"\\frac{x_7\\left<X,Y\\right>+3\\left<\\frac{A}{B}\\right>}{"
 		"\\left\\{\\frac{\\frac{2}{3}}{27}\\right\\}^2"
 	"}";