From 951f6115c16c3ab482c19705344295c90af1625b Mon Sep 17 00:00:00 2001
From: quou <quou@disroot.org>
Date: Sat, 27 Jul 2024 11:15:21 +1000
Subject: clipping and viewport improvements.

---
 3de.c    |  13 ++++++--
 maths.c  |   4 +--
 rect.c   |  44 +++++++++++++++++++++++++
 rect.h   |   2 ++
 render.c | 111 +++++++++++++++++++++++++++++++++++++++------------------------
 render.h |  10 ++++--
 6 files changed, 136 insertions(+), 48 deletions(-)

diff --git a/3de.c b/3de.c
index eb7a8f8..e18b643 100644
--- a/3de.c
+++ b/3de.c
@@ -43,6 +43,12 @@ void draw_tri(Renderer* r, int x, int y) {
 	ren_tri(r, v0, v1, v2, tex);
 }
 
+void draw_line(Renderer* r, int x, int y) {
+	int s[] = { 100, 100 };
+	int e[] = { x, y };
+	ren_line(r, make_red(), s, e);
+}
+
 int entrypoint(int argc, const char** argv, Arena* a) {
 	App* app;
 	Renderer r = { 0 };
@@ -83,10 +89,12 @@ int entrypoint(int argc, const char** argv, Arena* a) {
 	while (app->o) {
 		fps_begin(&f);
 		while (f.now >= f.next) {
+			Rect clip = { 30, 80, 400, 800 };
 			app_begin(app);
 			update_player(&p, &s);
 			ren_begin(&r, app->fb, depth, app->w, app->h);
-				ren_clear(&r);
+				ren_clip(&r, &clip);
+				ren_clearc(&r, make_blue());
 				ren_cleard(&r, f1 * 300);
 				sprintf(buf, "FPS: %d", app->fps);
 				ren_texts(&r, blue, 3, 3,  buf);
@@ -94,10 +102,11 @@ int entrypoint(int argc, const char** argv, Arena* a) {
 				ren_texts(&r, blue, 3, 8,  buf);
 				sprintf(buf, "MOUSE: %d, %d", app->mx, app->my);
 				ren_texts(&r, blue, 3, 13, buf);
+				draw_line(&r, app->mx, app->my);
 				push_player_cam(&p);
 				draw_gun(&r);
 				pop_player_cam();
-				/*draw_tri(&r, app->mx, app->my);*/
+				draw_tri(&r, app->mx, app->my);
 			ren_end(&r);
 			app_end(app);
 			fps_update(&f);
diff --git a/maths.c b/maths.c
index 706c12b..70b354e 100644
--- a/maths.c
+++ b/maths.c
@@ -290,8 +290,8 @@ int* persp(int* v, int asp) {
 }
 
 int* ndc2clip(const int* c, int* p) {
-	register int hw = c[2] >> 1;
-	register int hh = c[3] >> 1;
+	register int hw = c[0] >> 1;
+	register int hh = c[1] >> 1;
 	p[0] = ((hw << fbits) *  p[0]) >> fbits;
 	p[1] = ((hh << fbits) * -p[1]) >> fbits;
 	p[0] >>= fbits;
diff --git a/rect.c b/rect.c
index c72c66e..e3d3948 100644
--- a/rect.c
+++ b/rect.c
@@ -19,6 +19,24 @@ Rect* rect_clip(Rect* r, const Rect* c) {
 	return r;
 }
 
+Rect* rect_clipr(Rect* r, const int* c) {
+	int n;
+	int x = r->x, y = r->y;
+	if ((n = c[0] - r->x) > 0) {
+		r->w -= n;
+		r->x += n;
+	}
+	if ((n = c[1] - r->y) > 0) {
+		r->h -= n;
+		r->y += n;
+	}
+	if ((n = x + r->w - c[2]) > 0)
+		r->w -= n;
+	if ((n = y + r->h - c[3]) > 0)
+		r->h -= n;
+	return r;
+}
+
 Rect* rect_clips(Rect* r, Rect* s, const Rect* c) {
 	int n;
 	int x = r->x, y = r->y;
@@ -44,3 +62,29 @@ Rect* rect_clips(Rect* r, Rect* s, const Rect* c) {
 	}
 	return r;
 }
+
+Rect* rect_clipsr(Rect* r, Rect* s, const int* c) {
+	int n;
+	int x = r->x, y = r->y;
+	if ((n = c[0] - r->x) > 0) {
+		r->w -= n;
+		r->x += n;
+		s->w -= n;
+		s->x += n;
+	}
+	if ((n = c[1] - r->y) > 0) {
+		r->h -= n;
+		r->y += n;
+		s->h -= n;
+		s->y += n;
+	}
+	if ((n = x + r->w - c[2]) > 0) {
+		r->w -= n;
+		s->w -= n;
+	}
+	if ((n = y + r->h - c[3]) > 0) {
+		r->h -= n;
+		s->h -= n;
+	}
+	return r;
+}
diff --git a/rect.h b/rect.h
index b055607..74f3084 100644
--- a/rect.h
+++ b/rect.h
@@ -6,6 +6,8 @@ typedef struct {
 } Rect;
 
 Rect* rect_clip(Rect* r, const Rect* c);
+Rect* rect_clipr(Rect* r, const int* c);
 Rect* rect_clips(Rect* r, Rect* s, const Rect* c);
+Rect* rect_clipsr(Rect* r, Rect* s, const int* c);
 
 #endif
diff --git a/render.c b/render.c
index 233c084..c8b673b 100644
--- a/render.c
+++ b/render.c
@@ -149,17 +149,13 @@ Colour col_mul(Colour a, Colour b) {
 
 void ren_begin(Renderer* r, Colour* t, int* d, int w, int h) {
 	r->t = t;
-	r->vp[2] = w;
-	r->vp[3] = h;
+	r->vp[0] = w;
+	r->vp[1] = h;
 	r->d = d;
-	r->clip.x = 0;
-	r->clip.y = 0;
-	r->clip.w = w;
-	r->clip.h = h;
-	r->vp[0] = 0;
-	r->vp[1] = 0;
-	r->vp[2] = w;
-	r->vp[3] = h;
+	r->clip[0] = 0;
+	r->clip[1] = 0;
+	r->clip[2] = w;
+	r->clip[3] = h;
 	r->asp = (w << fbits) / h;
 	r->n = 256;
 }
@@ -169,36 +165,49 @@ void ren_end(Renderer* r) {
 }
 
 void ren_clear(Renderer* r) {
-	Colour* d = r->t, b = { 0 };
-	int i = 0, e = r->vp[2] * r->vp[3];
-	for (i = 0; i < e; i++, d++)
-		*d = b;
+	Colour c = { 0 };
+	ren_clearc(r, c);
 }
 
 void ren_clearc(Renderer* r, Colour c) {
-	Colour* d = r->t;
-	int i = 0, e = r->vp[2] * r->vp[3];
-	for (i = 0; i < e; i++, d++)
-		*d = c;
+	Colour* d = &r->t[r->clip[0] + r->clip[1] * r->vp[0]];
+	int s = r->vp[0] - (r->clip[2] - r->clip[0]), y;
+	for (y = r->clip[1]; y < r->clip[3]; y++) {
+		int x;
+		for (x = r->clip[0]; x < r->clip[2]; x++) {
+			*d = c;
+			d++;
+		}
+		d += s;
+	}
 }
 
 void ren_cleard(Renderer* r, int depth) {
-	int* d = r->d;
-	int i = 0, e = r->vp[2] * r->vp[3];
-	for (i = 0; i < e; i++, d++)
-		*d = depth;
+	int* d = &r->d[r->clip[0] + r->clip[1] * r->vp[0]];
+	int s = r->vp[0] - (r->clip[2] - r->clip[0]), y;
+	for (y = r->clip[1]; y < r->clip[3]; y++) {
+		int x;
+		for (x = r->clip[0]; x < r->clip[2]; x++) {
+			*d = depth;
+			d++;
+		}
+		d += s;
+	}
 }
 
 void ren_clip(Renderer* r, const Rect* c) {
-	r->clip = *c;
+	r->clip[0] = c->x;
+	r->clip[1] = c->y;
+	r->clip[2] = c->x + c->w;
+	r->clip[3] = c->y + c->h;
 }
 
 void ren_point(Renderer* r, Colour c, int x, int y) {
-	if (x < 0) return;
-	if (y < 0) return;
-	if (x >= r->vp[2]) return;
-	if (y >= r->vp[3]) return;
-	r->t[x + y * r->vp[2]] = c;
+	if (x <  r->clip[0]) return;
+	if (y <  r->clip[1]) return;
+	if (x >= r->clip[2]) return;
+	if (y >= r->clip[3]) return;
+	r->t[x + y * r->vp[0]] = c;
 }
 
 #define imp_ren_char(chw, chh, fw, data) \
@@ -209,11 +218,11 @@ void ren_point(Renderer* r, Colour c, int x, int y) {
 	re.x = x; \
 	re.y = y; \
 	sub.x = (ch - ' ') * chw; \
-	rect_clips(&re, &sub, &r->clip); \
+	rect_clipsr(&re, &sub, r->clip); \
 	ex = re.x + re.w; \
 	ey = re.y + re.h; \
-	dst = r->t + (re.x + re.y * r->vp[2]); \
-	s = r->vp[2] - re.w; \
+	dst = r->t + (re.x + re.y * r->vp[0]); \
+	s = r->vp[0] - re.w; \
 	for (j = re.y, l = sub.y; j < ey; j++, l++) { \
 		for (i = re.x, k = sub.x; i < ex; i++, k++) { \
 			int si = k + l * fw; \
@@ -416,6 +425,24 @@ void step_line(
 	}
 }
 
+void ren_line(
+	Renderer* r,
+	Colour c,
+	const int* s,
+	const int* e
+) {
+	Line l;
+	init_line(&l, s, e);
+	while (l.x != e[0] && l.y != e[1]) {
+		Colour* dst = &r->t[l.x + l.y * r->vp[0]];
+		if (l.x <  r->clip[0] || l.y <  r->clip[1]) goto step;
+		if (l.x >= r->clip[2] || l.y >= r->clip[3]) goto step;
+		*dst = blend(*dst, c);
+step:
+		step_line(&l);
+	}
+}
+
 void ren_tri(
 	Renderer* r,
 	const int* iv0,
@@ -426,8 +453,8 @@ void ren_tri(
 #define ic 6
 #define ec 8
 	int ha, i;
-	const int fcx = r->clip.x + r->clip.w;
-	const int fcy = r->clip.y + r->clip.h;
+	const int fcx = r->clip[2];
+	const int fcy = r->clip[3];
 	int v0[ec], v1[ec], v2[ec];
 	Line ne, fe; /* near and far edges */
 	Line ni[ic], fi[ic]; /* near and far interpolants */
@@ -478,7 +505,7 @@ void ren_tri(
 	if (v1[1] > fcy) v1[1] = fcy;
 #define scanline\
 		int x, ex = mini(fe.x, fcx);\
-		if (fe.y >= r->clip.y) { \
+		if (fe.y >= r->clip[1]) { \
 			for (i = 0; i < ic; i++)\
 				init_lerp(\
 					&xi[i],\
@@ -487,17 +514,17 @@ void ren_tri(
 				);\
 			for (x = ne.x; x < ex; x++) {\
 				Colour col;\
-				if (x >= r->clip.x) { \
+				if (x >= r->clip[0]) { \
 					col.r = (xi[3].x * 255) >> fbits;\
 					col.g = (xi[4].x * 255) >> fbits;\
 					col.b = (xi[5].x * 255) >> fbits;\
 					col.a = 0xff;\
-					if (xi[0].x < r->d[x + fe.y * r->vp[2]]) { \
-						r->t[x + fe.y * r->vp[2]] =	col_mul(\
+					if (xi[0].x < r->d[x + fe.y * r->vp[0]]) { \
+						r->t[x + fe.y * r->vp[0]] =	col_mul(\
 							sample_tex(tex, xi[1].x, xi[2].x),\
 							col\
 						);\
-						r->d[x + fe.y * r->vp[2]] = xi[0].x; \
+						r->d[x + fe.y * r->vp[0]] = xi[0].x; \
 					} \
 				} \
 				for (i = 0; i < ic; i++)\
@@ -605,10 +632,10 @@ int point_os(
 	int y
 ) {
 	return
-		x >= r->vp[0] &&
-		y >= r->vp[1] &&
-		x <  r->vp[2] &&
-		y <  r->vp[3];
+		x >= r->clip[0] &&
+		y >= r->clip[1] &&
+		x <  r->clip[2] &&
+		y <  r->clip[3];
 }
 
 void ren_mesh(
diff --git a/render.h b/render.h
index 996ba37..2299a30 100644
--- a/render.h
+++ b/render.h
@@ -42,8 +42,8 @@ typedef struct {
 	Colour* t;
 	int* d;
 	int asp, n;
-	int vp[4];
-	Rect clip;
+	int vp[2];
+	int clip[4];
 } Renderer;
 
 int tri_os(
@@ -95,6 +95,12 @@ void ren_texts(
 	int y,
 	const char* t
 );
+void ren_line(
+	Renderer* r,
+	Colour c,
+	const int* s,
+	const int* e
+);
 /* Vertex format:
  * x y z u v r g b
  * All fixed point values with 9 bits of precision.
-- 
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