70 lines
1.4 KiB
C
70 lines
1.4 KiB
C
#include <kernel/util/draw.h>
|
|
#include <kernel/util/atomic.h>
|
|
|
|
/* kvram_reverse() - Reverse Video RAM area */
|
|
void kvram_reverse(int x, int y, int width, int height)
|
|
{
|
|
extern uint32_t vram[256];
|
|
int vram_offset_y;
|
|
int j;
|
|
|
|
// Check error.
|
|
if (width < 0 || height < 0)
|
|
return;
|
|
|
|
// Get "real" X position and area width.
|
|
if (x < 0)
|
|
{
|
|
width = width + x;
|
|
x = 0;
|
|
} else {
|
|
if (x + width >= DISPLAY_SCREEN_WIDTH)
|
|
width = DISPLAY_SCREEN_WIDTH - x;
|
|
}
|
|
|
|
// Get "real" Y position and area height.
|
|
if (y < 0)
|
|
{
|
|
height = height + x;
|
|
y = 0;
|
|
} else {
|
|
if (y + height >= DISPLAY_SCREEN_HEIGHT)
|
|
height = DISPLAY_SCREEN_HEIGHT - x;
|
|
}
|
|
|
|
// Check potential error.
|
|
// @note we do not check height because the while()
|
|
// while do the job for us.
|
|
if (width < 0)
|
|
return;
|
|
|
|
// Generate VRAM offset for Y axis.
|
|
// @note:
|
|
// The screen width size is always 128 and we
|
|
// use 4-aligned Video RAM so 32 pixels per "slot"
|
|
// and 128 / 32 = 4.
|
|
// y * 4 can be optimised by used shift operator,
|
|
// this is why we use y << 2 because 2^2 = 4.
|
|
vram_offset_y = (y + height - 1) << 2;
|
|
|
|
|
|
// The Video RAM is sheared between each
|
|
// process and the kernel, so we should
|
|
// use atomic operation when we use it.
|
|
atomic_start();
|
|
|
|
// Reverse area
|
|
while (--height >= 0)
|
|
{
|
|
j = width + x;
|
|
while (--j >= x)
|
|
{
|
|
vram[(j >> 5) + vram_offset_y] ^= 0x80000000 >> (j & 31);
|
|
}
|
|
vram_offset_y = vram_offset_y - 4;
|
|
}
|
|
|
|
// End of atomic operation
|
|
atomic_stop();
|
|
}
|