Bug [#1588]. Round caret positions to the pixel grid instead of truncating.

This may move the caret to the right 1 pixel in some situations. While sometimes this
appears a little worse, on average it is slightly better than the precious code, with
carets appearing inside the previous character less often.

2 files changed, 13 insertions, 4 deletions

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index b1b25eb45..225c18cda 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -470,6 +470,11 @@
 	<a href="http://sourceforge.net/p/scintilla/bugs/1585/">Bug #1585</a>.
 	</li>
 	<li>
+	Caret positioning changed a little to appear inside characters less often by
+	rounding the caret position to the pixel grid instead of truncating.
+	<a href="http://sourceforge.net/p/scintilla/bugs/1588/">Bug #1588</a>.
+	</li>
+	<li>
 	Bug fixed where automatic indentation wrong when caret in virtual space.
 	<a href="http://sourceforge.net/p/scintilla/bugs/1586/">Bug #1586</a>.
 	</li>
diff --git a/src/Editor.cxx b/src/Editor.cxx
index c340bedf2..6c29e7100 100644
--- a/src/Editor.cxx
+++ b/src/Editor.cxx
@@ -88,6 +88,10 @@ Timer::Timer() :
 Idler::Idler() :
 		state(false), idlerID(0) {}
 
+static int RoundXYPosition(XYPOSITION xyPos) {
+	return int(xyPos+0.5);
+}
+
 static inline bool IsControlCharacter(int ch) {
 	// iscntrl returns true for lots of chars > 127 which are displayable
 	return ch >= 0 && ch < ' ';
@@ -3417,7 +3421,7 @@ void Editor::DrawCarets(Surface *surface, ViewStyle &vsDraw, int lineDoc, int xS
 				bool caretAtEOL = false;
 				bool drawBlockCaret = false;
 				XYPOSITION widthOverstrikeCaret;
-				int caretWidthOffset = 0;
+				XYPOSITION caretWidthOffset = 0;
 				PRectangle rcCaret = rcLine;
 
 				if (posCaret.Position() == pdoc->Length()) {   // At end of document
@@ -3433,11 +3437,11 @@ void Editor::DrawCarets(Surface *surface, ViewStyle &vsDraw, int lineDoc, int xS
 					widthOverstrikeCaret = 3;
 
 				if (xposCaret > 0)
-					caretWidthOffset = 1;	// Move back so overlaps both character cells.
+					caretWidthOffset = 0.51f;	// Move back so overlaps both character cells.
 				xposCaret += xStart;
 				if (posDrag.IsValid()) {
 					/* Dragging text, use a line caret */
-					rcCaret.left = xposCaret - caretWidthOffset;
+					rcCaret.left = RoundXYPosition(xposCaret - caretWidthOffset);
 					rcCaret.right = rcCaret.left + vsDraw.caretWidth;
 				} else if (inOverstrike && drawOverstrikeCaret) {
 					/* Overstrike (insert mode), use a modified bar caret */
@@ -3455,7 +3459,7 @@ void Editor::DrawCarets(Surface *surface, ViewStyle &vsDraw, int lineDoc, int xS
 					}
 				} else {
 					/* Line caret */
-					rcCaret.left = xposCaret - caretWidthOffset;
+					rcCaret.left = RoundXYPosition(xposCaret - caretWidthOffset);
 					rcCaret.right = rcCaret.left + vsDraw.caretWidth;
 				}
 				ColourDesired caretColour = mainCaret ? vsDraw.caretcolour : vsDraw.additionalCaretColour;