00884f28e2
The problem to fix is that the arrow drawn by draw_arrow1() in src/fl_symbols.cxx displays a faint clear line between the stem and head of the arrow with the Cairo graphics driver. This occurs because draw_arrow1() draws the arrow in 2 steps (a rectangle + a triangle) and the Cairo driver is configured to use antialiasing when filling polygons. The antialiasing produces the faint line between stem and head. Why does draw_arrow1() draw a rectangle + a triangle rather than a 7-vertex polygon? That's because the X11 graphics driver fails with its polygon- drawing function when the polygon is also rotated: the polygon is drawn empty. We want to keep using antialiasing under Cairo for polygons because the result is better with non horizontal/vertical polygon edges. This implementation changes function draw_arrow1() which draws the arrow as a 7-vertex filled polygon except when the graphics driver returns false for its virtual member function can_fill_non_convex_polygon(). In that situation, draw_arrow1() draws, as before, a rectangle + a triangle. The new, virtual member function can_fill_non_convex_polygon() returns true except for the X11 graphics driver. Therefore, draw_arrow1() is effectively unchanged under the X11 driver.
95 lines
2.4 KiB
C++
95 lines
2.4 KiB
C++
//
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// Portable drawing routines for the Fast Light Tool Kit (FLTK).
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//
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// Copyright 1998-2022 by Bill Spitzak and others.
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//
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// This library is free software. Distribution and use rights are outlined in
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// the file "COPYING" which should have been included with this file. If this
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// file is missing or damaged, see the license at:
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//
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// https://www.fltk.org/COPYING.php
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//
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// Please see the following page on how to report bugs and issues:
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//
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// https://www.fltk.org/bugs.php
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//
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/**
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\file Fl_Xlib_Graphics_Driver_vertex.cxx
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\brief Portable drawing code for drawing arbitrary shapes with
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simple 2D transformations, implemented for X11 Xlib.
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*/
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#include <config.h>
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#include "Fl_Xlib_Graphics_Driver.H"
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#include <FL/fl_draw.H>
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#include <FL/platform.H>
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#include <FL/math.h>
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void Fl_Xlib_Graphics_Driver::end_points() {
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if (n>1) XDrawPoints(fl_display, fl_window, gc_, short_point, n, 0);
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}
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void Fl_Xlib_Graphics_Driver::end_line() {
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if (n < 2) {
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end_points();
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return;
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}
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if (n>1) XDrawLines(fl_display, fl_window, gc_, short_point, n, 0);
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}
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void Fl_Xlib_Graphics_Driver::end_loop() {
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fixloop();
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if (n>2) {
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transformed_vertex0(short_point[0].x , short_point[0].y );
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}
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end_line();
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}
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void Fl_Xlib_Graphics_Driver::end_polygon() {
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fixloop();
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if (n < 3) {
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end_line();
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return;
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}
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if (n>2) XFillPolygon(fl_display, fl_window, gc_, short_point, n, Convex, 0);
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}
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void Fl_Xlib_Graphics_Driver::gap() {
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while (n>gap_+2 && short_point[n-1].x == short_point[gap_].x && short_point[n-1].y == short_point[gap_].y) n--;
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if (n > gap_+2) {
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transformed_vertex0(short_point[gap_].x, short_point[gap_].y);
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gap_ = n;
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} else {
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n = gap_;
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}
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}
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void Fl_Xlib_Graphics_Driver::end_complex_polygon() {
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gap();
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if (n < 3) {
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end_line();
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return;
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}
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if (n>2) XFillPolygon(fl_display, fl_window, gc_, short_point, n, 0, 0);
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}
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bool Fl_Xlib_Graphics_Driver::can_fill_non_convex_polygon() {
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return false;
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}
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// shortcut the closed circles so they use XDrawArc:
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// warning: these do not draw rotated ellipses correctly!
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// See fl_arc.c for portable version.
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void Fl_Xlib_Graphics_Driver::ellipse_unscaled(double xt, double yt, double rx, double ry) {
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int llx = (int)rint(xt-rx);
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int w = (int)rint(xt+rx)-llx;
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int lly = (int)rint(yt-ry);
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int h = (int)rint(yt+ry)-lly;
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(what == POLYGON ? XFillArc : XDrawArc)
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(fl_display, fl_window, gc_, llx, lly, w, h, 0, 360*64);
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}
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