From 71fba1c1de9509ed8e7a4db712f6b535fa1f1514 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Thu, 8 Jun 2023 22:27:52 +0100
Subject: Add blit rectangle

Allows blitting a section of a larger sprite.
---
 src/vga.c | 19 +++++++++++++++++++
 src/vga.h |  2 ++
 2 files changed, 21 insertions(+)

(limited to 'src')

diff --git a/src/vga.c b/src/vga.c
index 6b093c0..0df25f8 100644
--- a/src/vga.c
+++ b/src/vga.c
@@ -101,6 +101,25 @@ void blit(const uint8_t *sprite, const Rect *dst)
         }
 }
 
+void blitrc(const uint8_t *sprite, const Rect *src, const Rect *dst)
+{
+    for (int32_t j = dst->y * 320, sy = src->y * src->w; j < (dst->y + dst->h) * 320; j += 320, sy += src->w)
+        for (int16_t i = dst->x, sx = src->x; i < dst->x + dst->w; i++, sx++)
+        {
+            uint8_t b = sprite[sx + sy];
+
+            /* transparent */
+            if (b == TRANSPARENT)
+                continue;
+
+            /* clipping */
+            if (i < 0 || i >= 320 || j < 0 || j >= 200 * 320)
+                continue;
+
+            buffer[i + j] = b;
+        }
+}
+
 void blit_erase(uint8_t c)
 {
     memset(buffer, c, 320 * 200);
diff --git a/src/vga.h b/src/vga.h
index 8dae83d..40dbcdf 100644
--- a/src/vga.h
+++ b/src/vga.h
@@ -21,6 +21,8 @@ void wait_vsync();
 void set_palette(const uint8_t *palette);
 
 void blit(const uint8_t *sprite, const Rect *dst);
+/* in src w is sprite width, h is sprite height */
+void blitrc(const uint8_t *sprite, const Rect *src, const Rect *dst);
 void blit_erase(uint8_t c);
 void blit_update();
 
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