rescale the fbo so it’s always rendered pixel perfectly

src/fbo.c

@@ -10,8 +10,7 @@
 
 static float sanitize_scale(float scale) {
 	// return ftopow2(clamp(scale, 0.25, 4.0));
-	scale = max(0.1, scale);
-	return ((int)(scale*VIEWPORT_W*VIEWPORT_H+0.9999))/(float)VIEWPORT_W/VIEWPORT_H;
+	return max(0.1, scale);
 }
 
 void init_fbo(FBO *fbo, float scale) {
@@ -70,15 +69,15 @@ void delete_fbo(FBO *fbo) {
 }
 
 void draw_fbo(FBO *fbo) {
-	float wq = (fbo->scale*VIEWPORT_W)/(float)fbo->nw;
-	float hq = (fbo->scale*VIEWPORT_H)/(float)fbo->nh;
+	float wq = floor(fbo->scale*VIEWPORT_W)/(float)fbo->nw;
+	float hq = floor(fbo->scale*VIEWPORT_H)/(float)fbo->nh;
 	glMatrixMode(GL_TEXTURE);
 	glLoadIdentity();
 	glScalef(wq, hq, 1);
 	glMatrixMode(GL_MODELVIEW);
 
 	glPushMatrix();
-		glTranslatef(VIEWPORT_W/2, VIEWPORT_H/2, 0);
+		glTranslatef(VIEWPORT_W/2., VIEWPORT_H/2., 0);
 		glScalef(VIEWPORT_W, VIEWPORT_H, 1);
 		glEnable(GL_TEXTURE_2D);
 		glBindTexture(GL_TEXTURE_2D, fbo->tex);

src/stagedraw.c

@@ -264,9 +264,19 @@ static void postprocess_prepare(FBO *fbo, Shader *s) {
 }
 
 void stage_draw_foreground(void) {
+	int vw, vh;
+	video_get_viewport_size(&vw,&vh);
+
+	// CAUTION: Very intricate pixel perfect scaling that will ruin your day.
+	float facw = (float)vw/SCREEN_W;
+	float fach = (float)vh/SCREEN_H;
+	float scale = resources.fbo.fg[0].scale;
+
 	// draw the foreground FBO
 	glPushMatrix();
-		glTranslatef(VIEWPORT_X, VIEWPORT_Y, 0);
+		glScalef(1/facw,1/fach,1);
+		glTranslatef(floorf(facw*VIEWPORT_X), floorf(fach*VIEWPORT_Y), 0);
+		glScalef(floorf(scale*VIEWPORT_W)/VIEWPORT_W,floorf(scale*VIEWPORT_H)/VIEWPORT_H,1);
 		// apply the screenshake effect
 		if(global.shake_view) {
 			glTranslatef(global.shake_view*sin(global.frames),global.shake_view*sin(global.frames*1.1+3),0);
@@ -279,9 +289,9 @@ void stage_draw_foreground(void) {
 					global.shake_view = global.shake_view_fade = 0;
 			}
 		}
-
 		draw_fbo(&resources.fbo.fg[0]);
 	glPopMatrix();
+	set_ortho();
 }
 
 void stage_draw_scene(StageInfo *stage) {

src/video.c

@@ -49,7 +49,7 @@ static int video_compare_modes(const void *a, const void *b) {
 	return va->width * va->height - vb->width * vb->height;
 }
 
-void video_set_viewport(void) {
+void video_get_viewport_size(int *width, int *height) {
 	float w = video.current.width;
 	float h = video.current.height;
 	float r = w / h;
@@ -59,9 +59,17 @@ void video_set_viewport(void) {
 	} else if(r < VIDEO_ASPECT_RATIO) {
 		h = w / VIDEO_ASPECT_RATIO;
 	}
+	*width = w;
+	*height = h;
+}
+
+
+void video_set_viewport(void) {
+	int w, h;
+	video_get_viewport_size(&w,&h);
 
 	glClear(GL_COLOR_BUFFER_BIT);
-	glViewport((video.current.width - w) / 2, (video.current.height - h) / 2, (int)w, (int)h);
+	glViewport((video.current.width - w) / 2, (video.current.height - h) / 2, w, h);
 }
 
 void video_update_vsync(void) {
@@ -153,14 +161,9 @@ static void video_init_gl(void) {
 }
 
 static void video_update_quality(void) {
-	float q;
-	float r = (float)video.current.width / video.current.height;
-
-	if(r >= VIDEO_ASPECT_RATIO) {
-		q = (float)video.current.height / SCREEN_H;
-	} else {
-		q = (float)video.current.width / SCREEN_W;
-	}
+	int vw, vh;
+	video_get_viewport_size(&vw,&vh);
+	float q = (float)vh / SCREEN_H;
 
 	float fg = q * config_get_float(CONFIG_FG_QUALITY);
 	float bg = q * config_get_float(CONFIG_BG_QUALITY);

src/video.h

@@ -35,6 +35,7 @@ extern Video video;
 void video_init(void);
 void video_shutdown(void);
 void video_setmode(int w, int h, bool fs, bool resizable);
+void video_get_viewport_size(int *width, int *height);
 void video_set_viewport(void);
 bool video_isfullscreen(void);
 bool video_isresizable(void);