EXT-4625 - Chat bar doesn't display trailing character on some strings

reviewed by Leyla

2 files changed, 25 insertions, 5 deletions

diff --git a/indra/llrender/llfontgl.cpp b/indra/llrender/llfontgl.cpp
index 1de1d6ded4..b6a6b448ee 100644
--- a/indra/llrender/llfontgl.cpp
+++ b/indra/llrender/llfontgl.cpp
@@ -601,14 +601,20 @@ S32	LLFontGL::firstDrawableChar(const llwchar* wchars, F32 max_pixels, S32 text_
 	{
 		llwchar wch = wchars[i];
 
-		F32 char_width = mFontFreetype->getXAdvance(wch);
+		const LLFontGlyphInfo* fgi= mFontFreetype->getGlyphInfo(wch);
+
+		// last character uses character width, since the whole character needs to be visible
+		// other characters just use advance
+		F32 width = (i == start) 
+			? (F32)(fgi->mWidth + fgi->mXBearing)  	// use actual width for last character
+			: fgi->mXAdvance;						// use advance for all other characters										
 
-		if( scaled_max_pixels < (total_width + char_width) )
+		if( scaled_max_pixels < (total_width + width) )
 		{
 			break;
 		}
 
-		total_width += char_width;
+		total_width += width;
 		drawable_chars++;
 
 		if( max_chars >= 0 && drawable_chars >= max_chars )
@@ -626,7 +632,17 @@ S32	LLFontGL::firstDrawableChar(const llwchar* wchars, F32 max_pixels, S32 text_
 		total_width = llround(total_width);
 	}
 
-	return start_pos - drawable_chars;
+	if (drawable_chars == 0)
+	{
+		return start_pos; // just draw last character
+	}
+	else
+	{
+		// if only 1 character is drawable, we want to return start_pos as the first character to draw
+		// if 2 are drawable, return start_pos and character before start_pos, etc.
+		return start_pos + 1 - drawable_chars;
+	}
+	
 }
 
 S32 LLFontGL::charFromPixelOffset(const llwchar* wchars, S32 begin_offset, F32 target_x, F32 max_pixels, S32 max_chars, BOOL round) const
diff --git a/indra/llui/lllineeditor.cpp b/indra/llui/lllineeditor.cpp
index cb5aea272d..2cdcd3345e 100644
--- a/indra/llui/lllineeditor.cpp
+++ b/indra/llui/lllineeditor.cpp
@@ -422,12 +422,16 @@ void LLLineEditor::setCursor( S32 pos )
 	S32 old_cursor_pos = getCursor();
 	mCursorPos = llclamp( pos, 0, mText.length());
 
+	// position of end of next character after cursor
 	S32 pixels_after_scroll = findPixelNearestPos();
 	if( pixels_after_scroll > mTextRightEdge )
 	{
 		S32 width_chars_to_left = mGLFont->getWidth(mText.getWString().c_str(), 0, mScrollHPos);
 		S32 last_visible_char = mGLFont->maxDrawableChars(mText.getWString().c_str(), llmax(0.f, (F32)(mTextRightEdge - mTextLeftEdge + width_chars_to_left))); 
-		S32 min_scroll = mGLFont->firstDrawableChar(mText.getWString().c_str(), (F32)(mTextRightEdge - mTextLeftEdge), mText.length(), getCursor());
+		// character immediately to left of cursor should be last one visible (SCROLL_INCREMENT_ADD will scroll in more characters)
+		// or first character if cursor is at beginning
+		S32 new_last_visible_char = llmax(0, getCursor() - 1);
+		S32 min_scroll = mGLFont->firstDrawableChar(mText.getWString().c_str(), (F32)(mTextRightEdge - mTextLeftEdge), mText.length(), new_last_visible_char);
 		if (old_cursor_pos == last_visible_char)
 		{
 			mScrollHPos = llmin(mText.length(), llmax(min_scroll, mScrollHPos + SCROLL_INCREMENT_ADD));