# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1540773991 -3600
# Node ID 32cb6b232444bb6a0b045a6dbcfe94bb07e481b3
# Parent  812e66b7ad470985ebfe64a014c36f3bcb3ecbde
Improved the blitting code to permit saving and restoring framebuffer data and
for blitting with a key colour for transparency.
Introduced a sprite to test the blitting code.
Established a function to introduce delays in the example code.

diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga-dual/Makefile
--- a/examples/vga-dual/Makefile	Mon Oct 29 01:43:42 2018 +0100
+++ b/examples/vga-dual/Makefile	Mon Oct 29 01:46:31 2018 +0100
@@ -27,8 +27,8 @@
 
 # Ordering of objects is important and cannot be left to replacement rules.
 
-SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S
-OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o
+SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S
+OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o
 
 # Application-specific adjustments.
 # See: examples/vga/Makefile
diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga-dual/sprite.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/vga-dual/sprite.S	Mon Oct 29 01:46:31 2018 +0100
@@ -0,0 +1,1 @@
+../vga/sprite.S
\ No newline at end of file
diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga-pmp/Makefile
--- a/examples/vga-pmp/Makefile	Mon Oct 29 01:43:42 2018 +0100
+++ b/examples/vga-pmp/Makefile	Mon Oct 29 01:46:31 2018 +0100
@@ -27,8 +27,8 @@
 
 # Ordering of objects is important and cannot be left to replacement rules.
 
-SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S
-OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o
+SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S
+OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o
 
 # Application-specific adjustments.
 
diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga-pmp/sprite.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/vga-pmp/sprite.S	Mon Oct 29 01:46:31 2018 +0100
@@ -0,0 +1,1 @@
+../vga/sprite.S
\ No newline at end of file
diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga-timer/Makefile
--- a/examples/vga-timer/Makefile	Mon Oct 29 01:43:42 2018 +0100
+++ b/examples/vga-timer/Makefile	Mon Oct 29 01:46:31 2018 +0100
@@ -27,8 +27,8 @@
 
 # Ordering of objects is important and cannot be left to replacement rules.
 
-SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S
-OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o
+SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S
+OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o
 
 # Application-specific adjustments.
 # See: examples/vga/Makefile
diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga-timer/sprite.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/vga-timer/sprite.S	Mon Oct 29 01:46:31 2018 +0100
@@ -0,0 +1,1 @@
+../vga/sprite.S
\ No newline at end of file
diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga/Makefile
--- a/examples/vga/Makefile	Mon Oct 29 01:43:42 2018 +0100
+++ b/examples/vga/Makefile	Mon Oct 29 01:46:31 2018 +0100
@@ -27,8 +27,8 @@
 
 # Ordering of objects is important and cannot be left to replacement rules.
 
-SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S
-OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o
+SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S
+OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o
 
 # Application-specific adjustments.
 
diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga/main.c
--- a/examples/vga/main.c	Mon Oct 29 01:43:42 2018 +0100
+++ b/examples/vga/main.c	Mon Oct 29 01:46:31 2018 +0100
@@ -67,24 +67,32 @@
 
 extern uint8_t screendata[];
 extern uint32_t screendata_width, screendata_height;
+extern uint8_t sprite[];
+extern uint32_t sprite_width, sprite_height;
+
 
 
+/* Busy wait. */
+
+static void wait(uint32_t delay)
+{
+    uint32_t counter = delay;
+
+    if (!delay) return;
+    while (counter--) __asm__("");	/* retain loop */
+}
 
 /* Blink an attached LED with delays implemented using a loop. */
 
 static void blink(uint32_t delay, uint32_t port, uint32_t pins)
 {
-    uint32_t counter;
-
     /* Clear outputs (LED). */
 
     CLR_REG(port, pins);
 
     while (1)
     {
-        counter = delay;
-
-        while (counter--) __asm__("");	/* retain loop */
+        wait(delay);
 
         /* Invert outputs (LED). */
 
@@ -92,6 +100,31 @@
     }
 }
 
+/* Move a sprite around on the framebuffer. */
+
+static void animate(uint32_t delay)
+{
+    uint8_t background[sprite_width * sprite_height];
+    int x, y;
+
+    while (1)
+        for (y = 0; y < screendata_height - sprite_height; y++)
+            for (x = 0; x < screendata_width - sprite_width; x++)
+            {
+                /* Copy to the store from the display, then blit the image. */
+
+                copy_display(&display_config, background, sprite_width, sprite_height, x, y, -1, 0);
+                copy_display(&display_config, sprite, sprite_width, sprite_height, x, y, 0x8c, 1);
+
+                wait(delay);
+
+                /* Copy to the display from the store, restoring the original
+                   background. */
+
+                copy_display(&display_config, background, sprite_width, sprite_height, x, y, -1, 1);
+            }
+}
+
 
 
 /* Main program. */
@@ -136,8 +169,14 @@
 
     interrupts_on();
 
-    copy_to_framebuffer(&display_config, screendata, screendata_width, screendata_height);
-    blink(1 << 24, PORTA, LED_PIN);
+    /* Plot the image centred on the screen. */
+
+    copy_display(&display_config, screendata, screendata_width, screendata_height,
+         (LINE_LENGTH - screendata_width) / 2, (LINE_COUNT - screendata_height) / 2, -1, 1);
+
+    /* Move a sprite around on the screen with a delay between each movement. */
+
+    animate(1 << 24);
 }
 
 
diff -r 812e66b7ad47 -r 32cb6b232444 examples/vga/sprite.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/vga/sprite.S	Mon Oct 29 01:46:31 2018 +0100
@@ -0,0 +1,1425 @@
+.section .rodata, "a"
+
+/* Options:
+['-W', '48', '-H', '64', '-S', '-b']
+*/
+
+.globl sprite
+.globl sprite_width
+.globl sprite_height
+
+sprite_width:
+.word 22
+sprite_height:
+.word 64
+
+sprite:
+
+.byte 0x8c
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diff -r 812e66b7ad47 -r 32cb6b232444 include/display.h
--- a/include/display.h	Mon Oct 29 01:43:42 2018 +0100
+++ b/include/display.h	Mon Oct 29 01:46:31 2018 +0100
@@ -65,7 +65,10 @@
 /* Access functions. */
 
 int get_position(display_config_t *cfg, int x);
+
 void test_linedata(display_config_t *cfg);
-void copy_to_framebuffer(display_config_t *cfg, uint8_t *image, int width, int height);
+
+void copy_display(display_config_t *cfg, uint8_t *store, int width, int height,
+                  int x, int y, int key, int to_display);
 
 #endif /* __DISPLAY_H__ */
diff -r 812e66b7ad47 -r 32cb6b232444 lib/display.c
--- a/lib/display.c	Mon Oct 29 01:43:42 2018 +0100
+++ b/lib/display.c	Mon Oct 29 01:46:31 2018 +0100
@@ -55,21 +55,31 @@
     }
 }
 
-/* Copy to framebuffer. */
+/* Copying from/to the display to/from a backing store. */
 
-void copy_to_framebuffer(display_config_t *cfg, uint8_t *image, int width, int height)
+void copy_display(display_config_t *cfg, uint8_t *store, int width, int height,
+                  int x, int y, int key, int to_display)
 {
-    int sx, sy, tx, ty;
-    uint8_t *targetline = cfg->framebuffer, *sourceline = image;
+    int sx, sy, dx, dy;
+    uint8_t *storeline = store,
+            *displayline = cfg->framebuffer + y * cfg->line_length,
+            pixel;
 
-    for (sy = 0, ty = 0; (sy < height) && (ty < cfg->line_count); sy++, ty++)
+    for (sy = 0, dy = y; (sy < height) && (dy < cfg->line_count); sy++, dy++)
     {
-        for (sx = 0, tx = 0; (tx < cfg->line_length); sx++, tx++)
+        for (sx = 0, dx = x; (sx < width) && (dx < cfg->line_length); sx++, dx++)
         {
-            targetline[get_position(cfg, tx)] = (sx < width) ? sourceline[sx] : 0;
+            if (to_display)
+            {
+                pixel = storeline[sx];
+                if ((key < 0) || (pixel != key))
+                    displayline[get_position(cfg, dx)] = pixel;
+            }
+            else
+                storeline[sx] = displayline[get_position(cfg, dx)];
         }
 
-        sourceline += width;
-        targetline += cfg->line_length;
+        storeline += width;
+        displayline += cfg->line_length;
     }
 }