Fix drawing glitch when line width < 1px

1 files changed, 77 insertions, 1 deletions

diff --git a/tdegtk/tqtcairopainter.cpp b/tdegtk/tqtcairopainter.cpp
index d926541..8666b8b 100644
--- a/tdegtk/tqtcairopainter.cpp
+++ b/tdegtk/tqtcairopainter.cpp
@@ -756,6 +756,24 @@ void TQt3CairoPaintDevice::drawPolygon(const TQPointArray* pointarray, bool wind
 					cairo_close_path(FASTEST_AVAILABLE_PAINTER);
 				}
 				dualStrokePen();
+
+				// WARNING
+				// The Cairo anti-aliasing code fights back--HARD--when drawing 0px lines!
+				// See http://projecthamster.wordpress.com/2009/12/22/getting-sharp-pixels-and-actually-something-drawn-using-cairo/ for more details.
+				// This code works around the problem by overstriking the line end points with a single pixel, thereby ensuring they are properly drawn.
+				if (m_pen.width() < 1) {
+					cairo_save(FASTEST_AVAILABLE_PAINTER);
+					cairo_set_line_cap(FASTEST_AVAILABLE_PAINTER, CAIRO_LINE_CAP_ROUND);
+					cairo_set_line_join(FASTEST_AVAILABLE_PAINTER, CAIRO_LINE_JOIN_ROUND);
+					cairo_set_line_width(FASTEST_AVAILABLE_PAINTER, 1);
+					for (i=0;i<pointarray->count();i++) {
+						pointarray->point(i, &x, &y);
+						cairo_move_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
+						cairo_line_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
+					}
+					cairo_stroke(FASTEST_AVAILABLE_PAINTER);
+					cairo_restore(FASTEST_AVAILABLE_PAINTER);
+				}
 			}
 		}
 		cairo_restore(FASTEST_AVAILABLE_PAINTER);
@@ -1354,8 +1372,32 @@ bool TQt3CairoPaintDevice::cmd( int c, TQPainter *pt, TQPDevCmdParam *p )
 		if (FASTEST_AVAILABLE_PAINTER) {
 			cairo_save(FASTEST_AVAILABLE_PAINTER);
 			if (m_pen.style() != TQPen::NoPen) {
-				cairo_line_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
+				bool has_current_point = cairo_has_current_point(FASTEST_AVAILABLE_PAINTER);
+				double cr_x2;
+				double cr_y2;
+				cairo_get_current_point(FASTEST_AVAILABLE_PAINTER, &cr_x2, &cr_y2);
+				int x2 = cr_x2-CAIRO_PEN_PIXEL_OFFSET;
+				int y2 = cr_y2-CAIRO_PEN_PIXEL_OFFSET;
+
+				cairo_line_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
 				dualStrokePen();
+
+				// WARNING
+				// The Cairo anti-aliasing code fights back--HARD--when drawing 0px lines!
+				// See http://projecthamster.wordpress.com/2009/12/22/getting-sharp-pixels-and-actually-something-drawn-using-cairo/ for more details.
+				// This code works around the problem by overstriking the line end points with a single pixel, thereby ensuring they are properly drawn.
+				if (m_pen.width() < 1) {
+					cairo_save(FASTEST_AVAILABLE_PAINTER);
+					cairo_set_line_cap(FASTEST_AVAILABLE_PAINTER, CAIRO_LINE_CAP_ROUND);
+					cairo_set_line_join(FASTEST_AVAILABLE_PAINTER, CAIRO_LINE_JOIN_ROUND);
+					cairo_set_line_width(FASTEST_AVAILABLE_PAINTER, 1);
+					cairo_move_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
+					cairo_line_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
+					cairo_move_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
+					cairo_line_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
+					cairo_stroke(FASTEST_AVAILABLE_PAINTER);
+					cairo_restore(FASTEST_AVAILABLE_PAINTER);
+				}
 			}
 			cairo_restore(FASTEST_AVAILABLE_PAINTER);
 		}
@@ -1367,6 +1409,23 @@ bool TQt3CairoPaintDevice::cmd( int c, TQPainter *pt, TQPDevCmdParam *p )
 				cairo_move_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
 				cairo_line_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
 				dualStrokePen();
+
+				// WARNING
+				// The Cairo anti-aliasing code fights back--HARD--when drawing 0px lines!
+				// See http://projecthamster.wordpress.com/2009/12/22/getting-sharp-pixels-and-actually-something-drawn-using-cairo/ for more details.
+				// This code works around the problem by overstriking the line end points with a single pixel, thereby ensuring they are properly drawn.
+				if (m_pen.width() < 1) {
+					cairo_save(FASTEST_AVAILABLE_PAINTER);
+					cairo_set_line_cap(FASTEST_AVAILABLE_PAINTER, CAIRO_LINE_CAP_ROUND);
+					cairo_set_line_join(FASTEST_AVAILABLE_PAINTER, CAIRO_LINE_JOIN_ROUND);
+					cairo_set_line_width(FASTEST_AVAILABLE_PAINTER, 1);
+					cairo_move_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
+					cairo_line_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
+					cairo_move_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
+					cairo_line_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
+					cairo_stroke(FASTEST_AVAILABLE_PAINTER);
+					cairo_restore(FASTEST_AVAILABLE_PAINTER);
+				}
 			}
 			cairo_restore(FASTEST_AVAILABLE_PAINTER);
 		}
@@ -1459,6 +1518,23 @@ bool TQt3CairoPaintDevice::cmd( int c, TQPainter *pt, TQPDevCmdParam *p )
 							cairo_move_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
 							cairo_line_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
 							dualStrokePen();
+
+							// WARNING
+							// The Cairo anti-aliasing code fights back--HARD--when drawing 0px lines!
+							// See http://projecthamster.wordpress.com/2009/12/22/getting-sharp-pixels-and-actually-something-drawn-using-cairo/ for more details.
+							// This code works around the problem by overstriking the line end points with a single pixel, thereby ensuring they are properly drawn.
+							if (m_pen.width() < 1) {
+								cairo_save(FASTEST_AVAILABLE_PAINTER);
+								cairo_set_line_cap(FASTEST_AVAILABLE_PAINTER, CAIRO_LINE_CAP_ROUND);
+								cairo_set_line_join(FASTEST_AVAILABLE_PAINTER, CAIRO_LINE_JOIN_ROUND);
+								cairo_set_line_width(FASTEST_AVAILABLE_PAINTER, 1);
+								cairo_move_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
+								cairo_line_to(FASTEST_AVAILABLE_PAINTER, x+CAIRO_PEN_PIXEL_OFFSET, y+CAIRO_PEN_PIXEL_OFFSET);
+								cairo_move_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
+								cairo_line_to(FASTEST_AVAILABLE_PAINTER, x2+CAIRO_PEN_PIXEL_OFFSET, y2+CAIRO_PEN_PIXEL_OFFSET);
+								cairo_stroke(FASTEST_AVAILABLE_PAINTER);
+								cairo_restore(FASTEST_AVAILABLE_PAINTER);
+							}
 						}
 					}
 				}