teach begin_draw_texture to draw an arbitrary fragment

this is a tiny intermediate step towards a more flexible sprite system

it also seems to improve performance a little bit, though that's moot
since we're going to rewrite this part later together with most of the
rendering code anyway.

src/aniplayer.c

@@ -101,6 +101,7 @@ void aniplayer_update(AniPlayer *plr) {
 void play_animation_frame(Animation *ani, float x, float y, int frame) {
 	int mirror = frame/(ani->cols*ani->rows);
 	frame = frame%(ani->cols*ani->rows);
+
 	if(mirror) {
 		glPushMatrix();
 		glCullFace(GL_FRONT);

src/resource/animation.c

@@ -99,30 +99,15 @@ void draw_animation(float x, float y, int col, int row, const char *name) {
 }
 
 void draw_animation_p(float x, float y, int col, int row, Animation *ani) {
-	glBindTexture(GL_TEXTURE_2D, ani->tex->gltex);
+	float frame_w = (float)ani->tex->w / ani->cols;
+	float frame_h = (float)ani->tex->h / ani->rows;
 
-	float s = (float)ani->tex->w/ani->cols/ani->tex->truew;
-	float t = ((float)ani->tex->h)/ani->tex->trueh/(float)ani->rows;
-
-	glPushMatrix();
-	if(x || y)
-		glTranslatef(x,y,0);
-	if(ani->w != 1 || ani->h != 1)
-		glScalef(ani->w,ani->h, 1);
-
-	glMatrixMode(GL_TEXTURE);
-		glPushMatrix();
-		glScalef(s,t,1);
-
-		if(col || row)
-			glTranslatef(col, row, 0);
-	glMatrixMode(GL_MODELVIEW);
+	begin_draw_texture(
+		(FloatRect){ x, y, ani->w, ani->h },
+		(FloatRect){ col*frame_w, row*frame_h, frame_w, frame_h },
+		ani->tex
+	);
 
 	draw_quad();
-
-	glMatrixMode(GL_TEXTURE);
-		glPopMatrix();
-	glMatrixMode(GL_MODELVIEW);
-
-	glPopMatrix();
+	end_draw_texture();
 }

src/resource/texture.c

@@ -309,54 +309,81 @@ void draw_texture(float x, float y, const char *name) {
 	draw_texture_p(x, y, get_tex(name));
 }
 
-void begin_draw_texture(float x, float y, float w, float h, Texture *tex) {
+static struct draw_texture_state {
+	bool drawing;
+	bool texture_matrix_tainteed;
+} draw_texture_state;
+
+void begin_draw_texture(FloatRect dest, FloatRect frag, Texture *tex) {
+	if(draw_texture_state.drawing) {
+		log_fatal("Already drawing. Did you forget to call end_draw_texture, or call me on the wrong thread?");
+	}
+
+	draw_texture_state.drawing = true;
+
 	glBindTexture(GL_TEXTURE_2D, tex->gltex);
 	glPushMatrix();
 
-	float wq = ((float)tex->w)/tex->truew;
-	float hq = ((float)tex->h)/tex->trueh;
+	float x = dest.x;
+	float y = dest.y;
+	float w = dest.w;
+	float h = dest.h;
+
+	float s = frag.w/tex->truew;
+	float t = frag.h/tex->trueh;
+
+	if(s != 1 || t != 1 || frag.x || frag.y) {
+		draw_texture_state.texture_matrix_tainteed = true;
+
+		glMatrixMode(GL_TEXTURE);
+		glLoadIdentity();
+
+		glScalef(1.0/tex->truew, 1.0/tex->trueh, 1);
+
+		if(frag.x || frag.y) {
+			glTranslatef(frag.x, frag.y, 0);
+		}
+
+		if(s != 1 || t != 1) {
+			glScalef(frag.w, frag.h, 1);
+		}
+
+		glMatrixMode(GL_MODELVIEW);
+	}
 
 	if(x || y) {
 		glTranslatef(x, y, 0);
 	}
 
-	if(w == 0) {
-		w = tex->w;
-	}
-
-	if(h == 0) {
-		h = tex->h;
-	}
-
 	if(w != 1 || h != 1) {
 		glScalef(w, h, 1);
 	}
-
-	glMatrixMode(GL_TEXTURE);
-	glLoadIdentity();
-
-	if(wq != 1 || hq != 1) {
-		glScalef(wq, hq, 1);
-	}
-
-	glMatrixMode(GL_MODELVIEW);
 }
 
 void end_draw_texture(void) {
-	glMatrixMode(GL_TEXTURE);
-	glLoadIdentity();
-	glMatrixMode(GL_MODELVIEW);
+	if(!draw_texture_state.drawing) {
+		log_fatal("Not drawing. Did you forget to call begin_draw_texture, or call me on the wrong thread?");
+	}
+
+	if(draw_texture_state.texture_matrix_tainteed) {
+		draw_texture_state.texture_matrix_tainteed = false;
+		glMatrixMode(GL_TEXTURE);
+		glLoadIdentity();
+		glMatrixMode(GL_MODELVIEW);
+	}
+
 	glPopMatrix();
+	draw_texture_state.drawing = false;
 }
 
 void draw_texture_p(float x, float y, Texture *tex) {
-	begin_draw_texture(x, y, 0, 0, tex);
+	begin_draw_texture((FloatRect){ x, y, tex->w, tex->h }, (FloatRect){ 0, 0, tex->w, tex->h }, tex);
 	draw_quad();
 	end_draw_texture();
 }
 
 void draw_texture_with_size_p(float x, float y, float w, float h, Texture *tex) {
-	begin_draw_texture(x, y, w, h, tex);
+	begin_draw_texture((FloatRect){ x, y, w, h }, (FloatRect){ 0, 0, tex->w, tex->h }, tex);
 	draw_quad();
 	end_draw_texture();
 }

src/resource/texture.h

@@ -33,7 +33,7 @@ void free_texture(Texture *tex);
 void draw_texture(float x, float y, const char *name);
 void draw_texture_p(float x, float y, Texture *tex);
 
-void begin_draw_texture(float x, float y, float w, float h, Texture *tex);
+void begin_draw_texture(FloatRect dest, FloatRect frag, Texture *tex);
 void end_draw_texture(void);
 
 void draw_texture_with_size(float x, float y, float w, float h, const char *name);

src/util.c

@@ -364,7 +364,11 @@ void draw_stars(int x, int y, int numstars, int numfrags, int maxstars, int maxf
 	glUniform4fv(uniloc(shader, "back_color"), 1, clr);
 	glUniform1f(uniloc(shader, "fill"), 1);
 
-	begin_draw_texture(x - star_width, y, star_width, star_width, star);
+	begin_draw_texture(
+		(FloatRect){ x - star_width, y, star_width, star_width },
+		(FloatRect){ 0, 0, star->w, star->h },
+		star
+	);
 
 	while(i < numstars) {
 		glTranslatef(1, 0, 0);

src/util.h

@@ -62,6 +62,13 @@ char* ucs4_to_utf8(const uint32_t *ucs4);
 // math utils
 //
 
+typedef struct FloatRect {
+	float x;
+	float y;
+	float w;
+	float h;
+} FloatRect;
+
 #include <complex.h>
 
 // These definitions are common but non-standard, so we provide our own