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Fix bug in clipLine #32

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merged 1 commit into from May 4, 2018
Merged

Fix bug in clipLine #32

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58 changes: 28 additions & 30 deletions Pokitto/POKITTO_CORE/PokittoDisplay.cpp
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Expand Up @@ -853,61 +853,59 @@ void Display::drawLine(int16_t x0, int16_t y0, int16_t x1, int16_t y1) {

uint8_t Display::clipLine(int16_t *x0, int16_t *y0, int16_t *x1, int16_t *y1){
// Check X bounds
if (*x1<*x0) {
if (*x1 < *x0) {
//std::swap (*x1,*x0); // swap so that we dont have to check x1 also
swapWT(int16_t*,x1,x0);
swapWT(int16_t*, x1, x0);
//std::swap (*y1,*y0); // y needs to be swaaped also
swapWT(int16_t*,y1,y0);
swapWT(int16_t*, y1, y0);
}

if (*x0>=width) return 0; // whole line is out of bounds
if (*x0 >= width) return 0; // whole line is out of bounds

// Clip against X0 = 0
if (*x0 < 0) {
if ( *x1 < 0) return 0; // nothing visible
int16_t dx = (*x1 - *x0);
int16_t dy = ((*y1 - *y0) << 8); // 8.8 fixed point calculation trick
int16_t m = dy/dx;
*y0 = *y0 + ((m*-*x0)>>8); // get y0 at boundary
if (*x1 < 0) return 0; // nothing visible
int32_t dx = (*x1 - *x0);
int32_t dy = ((*y1 - *y0) << 16); // 16.16 fixed point calculation trick
int32_t m = dy/dx;
*y0 = *y0 + ((m*-*x0) >> 16); // get y0 at boundary
*x0 = 0;
}

// Clip against x1 = 83
// Clip against x1 >= width
if (*x1 >= width) {
int16_t dx = (*x1 - *x0);
int16_t dy = ((*y1 - *y0) << 8); // 8.8 fixed point calculation trick
int16_t m = dy/dx;
//*y1 = *y1 + ((m*(*x1-XMAX))>>8); // get y0 at boundary
*y1 = *y1 + ((m*(width-1-*x1))>>8); // get y0 at boundary
int32_t dx = (*x1 - *x0);
int32_t dy = ((*y1 - *y0) << 16); // 16.16 fixed point calculation trick
int32_t m = dy / dx;
*y1 = *y1 + ((m * ((width - 1) - *x1)) >> 16); // get y0 at boundary
*x1 = width-1;
}

// Check Y bounds
if (*y1<*y0) {
if (*y1 < *y0) {
//std::swap (*x1,*x0); // swap so that we dont have to check x1 also
swapWT(int16_t*,x1,x0);
swapWT(int16_t*, x1, x0);
//std::swap (*y1,*y0); // y needs to be swaaped also
swapWT(int16_t*,y1,y0);
swapWT(int16_t*, y1, y0);
}

if (*y0>=height) return 0; // whole line is out of bounds
if (*y0 >= height) return 0; // whole line is out of bounds

if (*y0 < 0) {
if ( *y1 < 0) return 0; // nothing visible
int16_t dx = (*x1 - *x0) << 8;
int16_t dy = (*y1 - *y0); // 8.8 fixed point calculation trick
int16_t m = dx/dy;
*x0 = *x0 + ((m*-*y0)>>8); // get x0 at boundary
if (*y1 < 0) return 0; // nothing visible
int32_t dx = (*x1 - *x0) << 16;
int32_t dy = (*y1 - *y0); // 16.16 fixed point calculation trick
int32_t m = dx / dy;
*x0 = *x0 + ((m * -(*y0)) >> 16); // get x0 at boundary
*y0 = 0;
}

// Clip against y1 = 47
// Clip against y1 >= height
if (*y1 >= height) {
int16_t dx = (*x1 - *x0) << 8;
int16_t dy = (*y1 - *y0); // 8.8 fixed point calculation trick
int16_t m = dx/dy;
*x1 = *x1 + ((m*(height-1-*y1))>>8); // get y0 at boundary
//*x1 = *x1 + ((m*(*y1-YMAX))>>8); // get y0 at boundary
int32_t dx = (*x1 - *x0) << 16;
int32_t dy = (*y1 - *y0); // 16.16 fixed point calculation trick
int32_t m = dx / dy;
*x1 = *x1 + ((m * ((height - 1) - *y1)) >> 16); // get y0 at boundary
*y1 = height-1;
}
return 1; // clipped succesfully
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