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KLN89: Fix clipping bug affecting the KLN89 map page. Pixels and lines must be clipped when being put into the buffer, since the clip region may change before the buffer is rendered. Also, the wrong DrawPixel function was called from the oldDrawLine function.

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This commit is contained in:
Dave Luff 2010-11-22 21:34:24 +00:00
parent 0b941b759a
commit cd420dadf7
1 changed files with 52 additions and 6 deletions
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58
src/Instrumentation/render_area_2d.cxx
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@ -145,7 +145,8 @@ void RenderArea2D::SetActualSize(int sizex, int sizey) {
}
void RenderArea2D::DrawPixel(int x, int y, bool invert) {
// Clipping is currently performed in oldDrawPixel - could clip here instead though.
// Clip
if(x < _clipx1 || x > _clipx2 || y < _clipy1 || y > _clipy2) return;
RA2DPrimitive prim;
prim.x1 = x;
@ -158,7 +159,10 @@ void RenderArea2D::DrawPixel(int x, int y, bool invert) {
}
void RenderArea2D::oldDrawPixel(int x, int y, bool invert) {
// Clip
// Clip. In theory this shouldn't be necessary, since all input is clipped before adding
// to the drawing list, but it ensures that any errors in clipping lines etc will only
// spill over the clip area within the instrument, and still be clipped from straying
// outside the instrument.
if(x < _clipx1 || x > _clipx2 || y < _clipy1 || y > _clipy2) return;
// Scale to position within background
@ -189,6 +193,46 @@ void RenderArea2D::oldDrawPixel(int x, int y, bool invert) {
}
void RenderArea2D::DrawLine(int x1, int y1, int x2, int y2) {
// We need to clip the line to the current region before storing it in the drawing
// list, since when we come to actually draw it the clip region may have changed.
// Liang-Barsky clipping algorithm
int p[4], q[4];
float u1 = 0.0f, u2 = 1.0f;
p[0] = -(x2 - x1); q[0] = (x1 - _clipx1);
p[1] = (x2 - x1); q[1] = (_clipx2 - x1);
p[2] = -(y2 - y1); q[2] = (y1 - _clipy1);
p[3] = (y2 - y1); q[3] = (_clipy2 - y1);
for(int i=0; i<4; ++i) {
if(p[i] == 0) {
if(q[i] < 0) {
// Then we have a trivial rejection of a line parallel to a clip plane
// completely outside the clip region.
return;
}
} else if(p[i] < 0) {
float r = (float)q[i]/(float)p[i];
u1 = (u1 > r ? u1 : r);
} else { // p[i] > 0
float r = (float)q[i]/(float)p[i];
u2 = (u2 < r ? u2 : r);
}
if(u1 > u2) {
// Then the line is completely outside the clip area.
return;
}
}
float fx1 = x1 + u1 * (float)(x2 - x1);
float fy1 = y1 + u1 * (float)(y2 - y1);
float fx2 = x1 + u2 * (float)(x2 - x1);
float fy2 = y1 + u2 * (float)(y2 - y1);
x1 = (int)(fx1 + 0.5);
y1 = (int)(fy1 + 0.5);
x2 = (int)(fx2 + 0.5);
y2 = (int)(fy2 + 0.5);
RA2DPrimitive prim;
prim.x1 = x1;
prim.y1 = y1;
@ -220,7 +264,7 @@ void RenderArea2D::oldDrawLine(int x1, int y1, int x2, int y2) {
int y = y1;
int yn = dx/2;
for(int x=x1; x<=x2; ++x) {
DrawPixel(x, y);
oldDrawPixel(x, y);
yn += dy;
if(yn >= dx) {
yn -= dx;
@ -234,7 +278,7 @@ void RenderArea2D::oldDrawLine(int x1, int y1, int x2, int y2) {
// Must be a more elegant way to roll the next two cases into one!
if(flip_y) {
for(int y=y1; y>=y2; --y) {
DrawPixel(x, y);
oldDrawPixel(x, y);
xn += dx;
if(xn >= dy) {
xn -= dy;
@ -243,7 +287,7 @@ void RenderArea2D::oldDrawLine(int x1, int y1, int x2, int y2) {
}
} else {
for(int y=y1; y<=y2; ++y) {
DrawPixel(x, y);
oldDrawPixel(x, y);
xn += dx;
if(xn >= dy) {
xn -= dy;
@ -255,7 +299,7 @@ void RenderArea2D::oldDrawLine(int x1, int y1, int x2, int y2) {
}
void RenderArea2D::DrawQuad(int x1, int y1, int x2, int y2, bool invert) {
// Clip and sanity-check.
// Force the input to be ordered with x1 < x2 and y1 < y2.
if(x1 > x2) {
int x = x2;
x2 = x1;
@ -266,6 +310,8 @@ void RenderArea2D::DrawQuad(int x1, int y1, int x2, int y2, bool invert) {
y2 = y1;
y1 = y;
}
// Clip the input to the current drawing region.
x1 = x1 < _clipx1 ? _clipx1 : x1;
if(x1 > _clipx2) { return; }
x2 = x2 > _clipx2 ? _clipx2 : x2;