Add assertions into blit(), discover an off-by-one bug and fix that bug.

src/datatypes/texture.c

@@ -11,12 +11,12 @@
 #include "texture.h"
 #include "color.h"
 #include "../utils/logging.h"
+#include "../utils/assert.h"
 
 //General-purpose blit function
 void blit(struct texture *t, struct color c, unsigned x, unsigned y) {
-	if ((x > t->width-1) || y < 0) return;
-	if ((y > t->height-1) || y < 0) return;
-
+	ASSERT(x < t->width); ASSERT(y < t->height);
+	ASSERT(x >= 0); ASSERT(y >= 0);
 	if (t->precision == char_p) {
 		t->byte_data[(x + (t->height - (y + 1)) * t->width) * t->channels + 0] = (unsigned char)min(c.red * 255.0, 255.0);
 		t->byte_data[(x + (t->height - (y + 1)) * t->width) * t->channels + 1] = (unsigned char)min(c.green * 255.0, 255.0);

src/renderer/renderer.c

@@ -211,8 +211,8 @@ void *renderThread(void *arg) {
 
 		while (tile.completedSamples < r->prefs.sampleCount+1 && r->state.isRendering) {
 			startTimer(&timer);
-			for (int y = (int)tile.end.y; y > (int)tile.begin.y; y--) {
-				for (int x = (int)tile.begin.x; x < (int)tile.end.x; x++) {
+			for (int y = tile.end.y - 1; y > tile.begin.y - 1; --y) {
+				for (int x = tile.begin.x; x < tile.end.x; ++x) {
 					if (r->state.renderAborted) return 0;
 					uint64_t pixIdx = y * image->width + x;
 					uint64_t uniqueIdx = pixIdx * r->prefs.sampleCount + tile.completedSamples;