From 760da5a3efd2e6ff166164a97a3b2cf3b6db6787 Mon Sep 17 00:00:00 2001
From: kdx <kikoodx@paranoici.org>
Date: Fri, 5 May 2023 19:37:28 +0200
Subject: z buffer

---
 src/main.c |  6 ++++--
 src/px.c   | 28 ++++++++++++++++++++++------
 src/px.h   |  5 ++++-
 3 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/src/main.c b/src/main.c
index 43c5d09..c3110a4 100644
--- a/src/main.c
+++ b/src/main.c
@@ -51,11 +51,13 @@ main(void)
 			if (pxbuf[i])
 				pxbuf[i] -= 1;
 
+		pxZ(1);
+		pxSpr(&spr, x, y);
+		pxZ(0);
+
 		pxRectfill(112, 112, x, y, 10);
 		pxRect(16, 16, x, y, 15);
 
-		pxSpr(&spr, x, y);
-
 		pxPal(3, 11);
 		pxPalt(3, true);
 		pxSpr(&spr, x, y + 8, .flip_x=true, .flip_y=true);
diff --git a/src/px.c b/src/px.c
index 694c789..267b2e0 100644
--- a/src/px.c
+++ b/src/px.c
@@ -4,6 +4,7 @@
 #include <assert.h>
 
 PxCol pxbuf[PX_WIDTH * PX_HEIGHT] = {0};
+unsigned int pxzbuf[PX_WIDTH * PX_HEIGHT] = {0};
 PxPal pxpal[256] = {
 	/* PICO-8 palette */
 	{0x00, 0x00, 0x00, false, 0, 0},
@@ -30,6 +31,7 @@ static struct {
 	int h;
 } pxclip = {0, 0, PX_WIDTH, PX_HEIGHT};
 static SDL_Texture *pxtexture = NULL;
+static unsigned int pxz = 0;
 
 int
 pxInit(void)
@@ -79,14 +81,18 @@ pxFlip(void)
 
 	SDL_UnlockTexture(pxtexture);
 	SDL_RenderCopy(___tzr_renderer, pxtexture, NULL, NULL);
+
+	return 0;
 }
 
 void
 pxCls(PxCol c)
 {
-	for (int y = 0; y < PX_HEIGHT; y++)
-		for (int x = 0; x < PX_WIDTH; x++)
-			pxPset(x, y, c);
+	for (int y = pxclip.y; y < pxclip.y + pxclip.h; y++)
+		for (int x = pxclip.x; x < pxclip.x + pxclip.w; x++) {
+			pxbuf[x + y * PX_WIDTH] = c;
+			pxzbuf[x + y * PX_WIDTH] = 0;
+		}
 }
 
 void
@@ -104,15 +110,25 @@ pxClipReset(void)
 	pxClip(0, 0, PX_WIDTH, PX_HEIGHT);
 }
 
+void
+pxZ(unsigned int z)
+{
+	pxz = z;
+}
+
 void
 pxPset(int x, int y, PxCol c)
 {
 	if (x < pxclip.x || x >= pxclip.x + pxclip.w ||
 	    y < pxclip.y || y >= pxclip.y + pxclip.h)
 		return;
-	if (pxpal[c].pal)
-		c = pxpal[c].pal - 1;
-	pxbuf[x + y * PX_WIDTH] = c;
+
+	/* z sorting */
+	if (pxz < pxzbuf[x + y * PX_WIDTH])
+		return;
+	pxzbuf[x + y * PX_WIDTH] = pxz;
+
+	pxbuf[x + y * PX_WIDTH] = pxpal[c].pal ? pxpal[c].pal : c;
 }
 
 uint8_t
diff --git a/src/px.h b/src/px.h
index cc59c7f..713f245 100644
--- a/src/px.h
+++ b/src/px.h
@@ -64,7 +64,7 @@ void pxDeinit(void);
 int pxFlip(void);
 
 /*** DRAW ***/
-/* Fill the clipping region with color 'c'. */
+/* Fill and reset Z on the clipping region with color 'c'. */
 void pxCls(PxCol c);
 
 /* Set the clipping region. */
@@ -73,6 +73,9 @@ void pxClip(int x, int y, int w, int h);
 /* Reset the clipping region. */
 void pxClipReset(void);
 
+/* Set Z layer. */
+void pxZ(unsigned int z);
+
 /* Put a pixel. */
 void pxPset(int x, int y, PxCol c);
 
-- 
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