# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1541872386 -3600
# Node ID 56b5497336325b89da4405aac3affc5ac2240a48
# Parent  005f2f8e6a61464615bc3577e3ae74307ac8ef1f
Introduced a sprite abstraction, bundling an image with stored display regions.

diff -r 005f2f8e6a61 -r 56b549733632 examples/vga/main.c
--- a/examples/vga/main.c	Sat Nov 10 17:58:49 2018 +0100
+++ b/examples/vga/main.c	Sat Nov 10 18:53:06 2018 +0100
@@ -116,21 +116,21 @@
 
 /* Copy to the store from the display, then blit the image. */
 
-static void plot_sprite(stored_regions_t *r, int x, int y, int key)
+static void plot_sprite(sprite_t *s, int x, int y, int key)
 {
     int frame = display_config.frame;
-    position_t *p = image_get_stored_position(r, frame);
+    position_t *p = image_get_stored_position(s->regions, frame);
 
     /* Copy to the stored region. */
 
-    display_copy(&display_config, image_get_stored_region(r, frame),
-                 sprite.width, sprite.height / SOURCE_YSTEP, 1,
+    display_copy(&display_config, image_get_stored_region(s->regions, frame),
+                 s->image->width, s->image->height / s->yscale, 1,
                  x, y, -1, 0);
 
     /* Plot to the screen. */
 
-    display_copy(&display_config, sprite.image,
-                 sprite.width, sprite.height, SOURCE_YSTEP,
+    display_copy(&display_config, s->image->image,
+                 s->image->width, s->image->height, s->yscale,
                  x, y, key, 1);
 
     /* Record the stored background details. */
@@ -138,20 +138,20 @@
     p->x = x;
     p->y = y;
 
-    if (frame >= r->stored)
-        r->stored = frame + 1;
+    if (frame >= s->regions->stored)
+        s->regions->stored = frame + 1;
 }
 
 /* Copy to the display from the store, restoring the original background. */
 
-static void unplot_sprite(stored_regions_t *r)
+static void unplot_sprite(sprite_t *s)
 {
     int frame = display_config.frame;
-    position_t *p = image_get_stored_position(r, frame);
+    position_t *p = image_get_stored_position(s->regions, frame);
 
-    if (r->stored > frame)
-        display_copy(&display_config, image_get_stored_region(r, frame),
-                     sprite.width, sprite.height / SOURCE_YSTEP, 1,
+    if (s->regions->stored > frame)
+        display_copy(&display_config, image_get_stored_region(s->regions, frame),
+                     s->image->width, s->image->height / s->yscale, 1,
                      p->x, p->y, -1, 1);
 }
 
@@ -232,7 +232,7 @@
 {
     /* Stores of background details, replotted when moving the sprite. */
 
-    Stored_Regions(regions, FRAME_COUNT, (sprite.width * sprite.height) / SOURCE_YSTEP);
+    Sprite(s, &sprite, FRAME_COUNT, SOURCE_YSTEP);
 
     /* Sprite position. */
 
@@ -260,11 +260,11 @@
 
     while (1)
     {
-        for (y = 0; y < display_config.line_count - sprite.height; y++)
+        for (y = 0; y < display_config.line_count - s.image->height; y++)
         {
-            for (x = 0; x < display_config.line_length - sprite.width; x++)
+            for (x = 0; x < display_config.line_length - s.image->width; x++)
             {
-                plot_sprite(&regions, x, y, 0x8c);
+                plot_sprite(&s, x, y, 0x8c);
 
                 /* Update the display with the frame details. */
 
@@ -277,7 +277,7 @@
 
                 /* Prepare the frame for updates. */
 
-                unplot_sprite(&regions);
+                unplot_sprite(&s);
 
                 /* Scroll in the indicated direction. */
 
diff -r 005f2f8e6a61 -r 56b549733632 include/image.h
--- a/include/image.h	Sat Nov 10 17:58:49 2018 +0100
+++ b/include/image.h	Sat Nov 10 18:53:06 2018 +0100
@@ -69,15 +69,39 @@
 
 
 
-/* Initialise stored regions, allocating memory and a structure to access it. */
+/* A simple sprite abstraction. */
+
+typedef struct
+{
+    /* The sprite image. */
+
+    image_t *image;
+
+    /* The stored regions to be used to unplot the sprite. */
+
+    stored_regions_t *regions;
+
+    /* The vertical scaling factor translating display rows to image
+       coordinates. */
+
+    int yscale;
 
-#define Stored_Regions(NAME, FRAMES, SIZE)      \
-    uint8_t __##NAME##_image[FRAMES * SIZE];    \
-    position_t __##NAME##_pos[FRAMES];          \
-    stored_regions_t NAME = {                   \
-        .image=__##NAME##_image,                \
-        .size=SIZE,                             \
-        .stored=0,                              \
+} sprite_t;
+
+
+
+/* Initialise stored regions, allocating memory and a structure to access it.
+
+   Stored_Regions(<name>, int, int)
+*/
+
+#define Stored_Regions(NAME, FRAMES, SIZE)          \
+    uint8_t __##NAME##_image[(FRAMES) * (SIZE)];    \
+    position_t __##NAME##_pos[FRAMES];              \
+    stored_regions_t NAME = {                       \
+        .image=__##NAME##_image,                    \
+        .size=SIZE,                                 \
+        .stored=0,                                  \
         .pos=__##NAME##_pos};
 
 /* Access functions. */
@@ -86,4 +110,20 @@
 
 uint8_t *image_get_stored_region(stored_regions_t *r, int frame);
 
+
+
+/* Initialise a sprite object using an existing image, creating stored regions
+   for the animation of the sprite.
+
+   Sprite(<name>, image_t *, int, int)
+*/
+
+#define Sprite(NAME, IMAGE, FRAMES, YSCALE)                         \
+    Stored_Regions(__##NAME##_regions, FRAMES,                      \
+                   (IMAGE)->width * (IMAGE)->height * (YSCALE));    \
+    sprite_t NAME = {                                               \
+        .image=IMAGE,                                               \
+        .regions=&(__##NAME##_regions),                             \
+        .yscale=YSCALE};
+
 #endif /* __IMAGE_H__ */