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[apps/curve_view] Fix drawArrow

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Compute everything in pixels + fix glitch when zooming on the tip of
arrow(0,0,2,3)
This commit is contained in:
Léa Saviot
2020-06-04 11:54:40 +02:00
committed by Émilie Feral
parent 2ebad3062c
commit 72e342e1b1
2 changed files with 32 additions and 26 deletions
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56
apps/shared/curve_view.cpp
View File

@@ -465,60 +465,66 @@ void CurveView::drawDot(KDContext * ctx, KDRect rect, float x, float y, KDColor
}
void CurveView::drawArrow(KDContext * ctx, KDRect rect, float x, float y, float dx, float dy, KDColor color, float arrowWith, float tanAngle) const {
/* TODO: all computations are done in pixels because doing them in float
* values led to approximation error (?). But this leads to useless back and
* forth between float and pixels. Find a proper way to handle approximation
* errors (if this was the problem). */
void CurveView::drawArrow(KDContext * ctx, KDRect rect, float x, float y, float dx, float dy, KDColor color, float arrowWidth, float tanAngle) const {
assert(tanAngle >= 0.0f);
if (std::fabs(dx) < FLT_EPSILON && std::fabs(dy) < FLT_EPSILON) {
// We can't draw an arrow without any orientation
return;
}
// Turn arrowWith in pixel length
float pixelArrowWith = 8.0f; // default value in pixels
if (arrowWith > 0.0f) {
float dxdy = std::sqrt(dx*dx+dy*dy);
float dxArrow = arrowWith*dx/dxdy;
float dyArrow = arrowWith*dy/dxdy;
pixelArrowWith = floatLengthToPixelLength(dxArrow, dyArrow);
// Translate arrowWidth in pixel length
float pixelArrowWidth = 8.0f; // default value in pixels
if (arrowWidth > 0.0f) {
float dxdyFloat = std::sqrt(dx * dx + dy * dy);
float dxArrowFloat = arrowWidth * std::fabs(dy) / dxdyFloat;
float dyArrowFloat = arrowWidth * std::fabs(dx) / dxdyFloat;
pixelArrowWidth = floatLengthToPixelLength(dxArrowFloat, dyArrowFloat);
assert(pixelArrowWidth > 0.0f);
}
/* Let's call the following variables L and l:
*
* / |
* /arrow2 |
* / |
* / l
* / |
* / |
* <--------------------------------------------------
* / B |
* <---------+----------------------------------------
* \
* \
* \
* \
* \
* \arrow1
*
* ----- L -----
*
*/
float l = pixelArrowWith/2.0;
float L = l/tanAngle;
float lPixel = pixelArrowWidth / 2.0;
float LPixel = lPixel / tanAngle;
float xPixel = floatToPixel(Axis::Horizontal, x);
float yPixel = floatToPixel(Axis::Vertical, y);
// We compute the arrow segments in pixels
float dxPixel = floatLengthToPixelLength(Axis::Horizontal, dx);
float dyPixel = floatLengthToPixelLength(Axis::Vertical, dy);
float dx2dy2Pixel = floatLengthToPixelLength(dx, dy);
float arrow1dx = pixelLengthToFloatLength(Axis::Horizontal, L*dxPixel/dx2dy2Pixel + l*dyPixel/dx2dy2Pixel);
float arrow1dy = pixelLengthToFloatLength(Axis::Vertical, L*dyPixel/dx2dy2Pixel - l*dxPixel/dx2dy2Pixel);
drawSegment(ctx, rect, x, y, x - arrow1dx, y - arrow1dy, color, false);
// Point B is the orthogonal projection of the arrow tips on the arrow body
float bxPixel = xPixel - LPixel * dxPixel / dx2dy2Pixel;
float byPixel = yPixel + LPixel * dyPixel / dx2dy2Pixel;
float arrow2dx = pixelLengthToFloatLength(Axis::Horizontal, L*dxPixel/dx2dy2Pixel - l*dyPixel/dx2dy2Pixel);
float arrow2dy = pixelLengthToFloatLength(Axis::Vertical, L*dyPixel/dx2dy2Pixel + l*dxPixel/dx2dy2Pixel);
drawSegment(ctx, rect, x, y, x - arrow2dx, y - arrow2dy, color, false);
float dxArrowPixel = - lPixel * dyPixel / dx2dy2Pixel;
float dyArrowPixel = lPixel * dxPixel / dx2dy2Pixel;
float arrow1xPixel = bxPixel + dxArrowPixel;
float arrow1yPixel = byPixel - dyArrowPixel;
float arrow2xPixel = bxPixel - dxArrowPixel;
float arrow2yPixel = byPixel + dyArrowPixel;
straightJoinDots(ctx, rect, xPixel, yPixel, arrow1xPixel, arrow1yPixel, color, true);
straightJoinDots(ctx, rect, xPixel, yPixel, arrow2xPixel, arrow2yPixel, color, true);
}
void CurveView::drawGrid(KDContext * ctx, KDRect rect) const {