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Rectangle border/sizing behaves like CSS border-box

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This commit is contained in:
Paul Davis 2018-11-25 19:08:51 -05:00
parent 27919fec61
commit b18aaf0c7c
1 changed files with 23 additions and 47 deletions
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70
libs/canvas/rectangle.cc
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@ -32,6 +32,21 @@
using namespace std;
using namespace ArdourCanvas;
/* Rectangle notes
*
* A Rectangle is defined by an ArdourCanvas::Rect which encloses every pixel
* that the Rectangle might draw. If the Rect is (0, 0, 10, 10) then a filled
* version of the Rectangle will paint every pixel up to and including those
* edges.
*
* If there is a border to the Rectangle, it will be drawn *INSIDE* the
* boundary given by the Rect. The border will include (at minimum) the outer
* pixel edge(s) of the Rectangle.
*
* This makes ArdourCanvas::Rectangle follow the semantics implied by CSS's
* box-sizing: border-box, rather than box-sizing: content-box
*/
Rectangle::Rectangle (Canvas* c)
: Item (c)
, _outline_what ((What) (LEFT | RIGHT | TOP | BOTTOM))
@ -69,7 +84,7 @@ Rectangle::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) con
part of item_to_canvas()
*/
Rect self (item_to_window (_rect, false));
Rect self (item_to_window (_rect));
const Rect draw = self.intersection (area);
if (!draw) {
@ -102,30 +117,19 @@ Rectangle::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) con
setup_outline_context (context);
/* the goal here is that if the border is 1 pixel
* thick, it will precisely align with the corner
* coordinates of the rectangle. So if the rectangle
* has a left edge at 0 and a right edge at 10, then
* the left edge must span 0..1, the right edge
* must span 10..11 because the first and final pixels
* to be colored are actually "at" 0.5 and 10.5 (midway
* between the integer coordinates).
*
* See the Cairo FAQ on single pixel lines for more
* detail.
*/
const double shift = _outline_width * 0.5;
self = self.translate (Duple (shift, shift));
if (fmod (_outline_width, 2.0) != 0.0) {
const double shift = _outline_width * 0.5;
self = self.translate (Duple (shift, shift));
if (name == "selection frame") {
std::cerr << "Render selection frame on " << self << std::endl;
}
if (_outline_what == What (LEFT|RIGHT|BOTTOM|TOP)) {
if (_corner_radius) {
Gtkmm2ext::rounded_rectangle (context, self.x0, self.y0, self.width(), self.height(), _corner_radius);
Gtkmm2ext::rounded_rectangle (context, self.x0, self.y0, self.width() - _outline_width, self.height() - _outline_width, _corner_radius);
} else {
context->rectangle (self.x0, self.y0, self.width(), self.height());
context->rectangle (self.x0, self.y0, self.width() - _outline_width, self.height() - _outline_width);
}
} else {
@ -172,35 +176,7 @@ void
Rectangle::compute_bounding_box () const
{
if (!_rect.empty()) {
Rect r = _rect.fix ();
/* if the outline is 1 pixel, then the actual
bounding box is 0.5 pixels outside the stated
corners of the rectangle.
if the outline is 2 pixels, then the actual
bounding box is 1.0 pixels outside the stated
corners of the rectangle (so that the middle
of the 2 pixel wide border passes through
the corners, alternatively described as 1 row
of pixels outside of the corners, and 1 row
inside).
if the outline is 3 pixels, then the actual
bounding box is 1.5 outside the stated corners
of the rectangle (so that the middle row of
pixels of the border passes through the corners).
if the outline is 4 pixels, then the actual bounding
box is 2.0 pixels outside the stated corners
of the rectangle, so that the border consists
of 2 pixels outside the corners and 2 pixels inside.
hence ... the bounding box is width * 0.5 larger
than the rectangle itself.
*/
_bounding_box = r.expand (1.0 + _outline_width * 0.5);
_bounding_box = _rect.fix().expand (_outline_width * 0.5);
}
_bounding_box_dirty = false;