render: add a dgetpixel() function

CMakeLists.txt

@@ -132,6 +132,7 @@ set(SOURCES_FX
   # Gray engine
   src/gray/engine.c
   src/gray/gclear.c
+  src/gray/ggetpixel.c
   src/gray/gint_gline.c
   src/gray/gpixel.c
   src/gray/grect.c
@@ -144,6 +145,7 @@ set(SOURCES_FX
   src/render-fx/bopti-asm.s
   src/render-fx/bopti.c
   src/render-fx/dclear.c
+  src/render-fx/dgetpixel.c
   src/render-fx/dpixel.c
   src/render-fx/drect.c
   src/render-fx/dsubimage.c
@@ -193,6 +195,7 @@ set(SOURCES_CG
   src/image/image_vflip_alloc.c
   # Rendering
   src/render-cg/dclear.c
+  src/render-cg/dgetpixel.c
   src/render-cg/dpixel.c
   src/render-cg/drect.c
   src/render-cg/dsubimage.c

TODO

@@ -1,3 +1,6 @@
+Bugs to fix:
+* render:    figure out why fx-CG dclear() now takes 4.1 ms instead of 2.6 ms
+
 Extensions on existing code:
 * clock:     mono support
 * usb:       add PC->calc reading, and interrupt pipes

include/gint/display.h

@@ -151,6 +151,11 @@ void drect_border(int x1, int y1, int x2, int y2,
    *: When the gray engine is on, see dgray(). */
 void dpixel(int x, int y, int color);
 
+/* dgetpixel(): Get a pixel's color
+   Returns the current color of any pixel in the VRAM. This function ignores
+   the rendering window. Returns -1 if (x,y) is out of bounds. */
+int dgetpixel(int x, int y);
+
 /* dline(): Render a straight line
 
    This function draws a line using a Bresenham-style algorithm. Please note

src/gray/engine.c

@@ -41,6 +41,7 @@ static struct rendering_mode const gray_mode = {
 	.dclear       = gclear,
 	.drect        = grect,
 	.dpixel       = gpixel,
+	.dgetpixel    = ggetpixel,
 	.gint_dhline  = gint_ghline,
 	.gint_dvline  = gint_gvline,
 	.dtext_opt    = gtext_opt,
@@ -51,6 +52,7 @@ static struct rendering_mode const gray_exit_mode = {
 	.dclear       = NULL,
 	.drect        = NULL,
 	.dpixel       = NULL,
+	.dgetpixel    = NULL,
 	.gint_dhline  = NULL,
 	.gint_dvline  = NULL,
 	.dtext_opt    = NULL,

src/gray/ggetpixel.c

@@ -0,0 +1,15 @@
+#include <gint/gray.h>
+#include <gint/defs/types.h>
+
+int ggetpixel(int x, int y)
+{
+	uint32_t *light, *dark;
+	dgray_getvram(&light, &dark);
+
+	int offset = (y << 2) + (x >> 5);
+	uint32_t mask = 1 << (~x & 31);
+
+	bool l = (light[offset] & mask) != 0;
+	bool d = (dark [offset] & mask) != 0;
+	return (d << 1) | l;
+}

src/render-cg/dgetpixel.c

@@ -0,0 +1,7 @@
+#include <gint/display.h>
+
+int dgetpixel(int x, int y)
+{
+	if((uint)x >= DWIDTH || (uint)y >= DHEIGHT) return -1;
+	return gint_vram[DWIDTH * y + x];
+}

src/render-fx/dgetpixel.c

@@ -0,0 +1,15 @@
+#include <gint/display.h>
+#include <gint/defs/types.h>
+#include "render-fx.h"
+
+int dgetpixel(int x, int y)
+{
+	if((uint)x >= DWIDTH || (uint)y >= DHEIGHT) return -1;
+
+	DMODE_OVERRIDE(dgetpixel, x, y);
+
+	int offset = (y << 2) + (x >> 5);
+	uint32_t mask = 1 << (~x & 31);
+
+	return (gint_vram[offset] & mask) ? C_BLACK : C_WHITE;
+}

src/render-fx/render-fx.h

@@ -69,6 +69,7 @@ struct rendering_mode
 	void (*drect)(int x1, int y1, int x2, int y2, color_t color);
 	/* Point rendering */
 	void (*dpixel)(int x, int y, color_t color);
+	int (*dgetpixel)(int x, int y);
 	void (*gint_dhline)(int x1, int x2, int y, int color);
 	void (*gint_dvline)(int y1, int y2, int x, int color);
 	/* Text and image rendering */
@@ -87,6 +88,7 @@ int gupdate(void);
 void gclear(color_t color);
 void grect(int x1, int y1, int x2, int y2, color_t color);
 void gpixel(int x, int y, color_t color);
+int ggetpixel(int x, int y);
 void gint_ghline(int x1, int x2, int y, int color);
 void gint_gvline(int y1, int y2, int x, int color);
 void gtext_opt(int x, int y, int fg, int bg, int halign, int valign,
@@ -96,8 +98,7 @@ void gsubimage(bopti_image_t const *image, struct rbox *r, int flags);
 /* Short macro to call the alternate rendering function when available */
 #define DMODE_OVERRIDE(func, ...)			\
 	if(dmode && dmode->func) {			\
-		dmode->func(__VA_ARGS__);	\
+		return dmode->func(__VA_ARGS__);	\
-		return;				\
 	}
 
 #endif /* RENDER_FX */