(svn r25651) -Fix: Textbuf caret rendering for complex scripts (e.g. Tamil).

src/gfx.cpp

@@ -707,6 +707,20 @@ Dimension GetStringBoundingBox(StringID strid)
 	return GetStringBoundingBox(buffer);
 }
 
+/**
+ * Get the leading corner of a character in a single-line string relative
+ * to the start of the string.
+ * @param str String containing the character.
+ * @param ch Pointer to the character in the string.
+ * @param start_fontsize Font size to start the text with.
+ * @return Upper left corner of the glyph associated with the character.
+ */
+Point GetCharPosInString(const char *str, const char *ch, FontSize start_fontsize)
+{
+	Layouter layout(str, INT32_MAX, TC_FROMSTRING, start_fontsize);
+	return layout.GetCharPosition(ch);
+}
+
 /**
  * Draw single character horizontally centered around (x,y)
  * @param c           Character (glyph) to draw

src/gfx_func.h

@@ -126,6 +126,7 @@ int GetStringLineCount(StringID str, int maxw);
 Dimension GetStringMultiLineBoundingBox(StringID str, const Dimension &suggestion);
 Dimension GetStringMultiLineBoundingBox(const char *str, const Dimension &suggestion);
 void LoadStringWidthTable(bool monospace = false);
+Point GetCharPosInString(const char *str, const char *ch, FontSize start_fontsize = FS_NORMAL);
 
 void DrawDirtyBlocks();
 void SetDirtyBlocks(int left, int top, int right, int bottom);

src/gfx_layout.cpp

@@ -423,7 +423,7 @@ ParagraphLayout *Layouter::GetParagraphLayout(WChar *buff, WChar *buff_end, Font
  * @param colour   The colour of the font.
  * @param fontsize The size of font to use.
  */
-Layouter::Layouter(const char *str, int maxw, TextColour colour, FontSize fontsize)
+Layouter::Layouter(const char *str, int maxw, TextColour colour, FontSize fontsize) : string(str)
 {
 	FontState state(colour, fontsize);
 	WChar c = 0;
@@ -512,6 +512,59 @@ Dimension Layouter::GetBounds()
 	return d;
 }
 
+/**
+ * Get the position of a character in the layout.
+ * @param ch Character to get the position of.
+ * @return Upper left corner of the character relative to the start of the string.
+ * @note Will only work right for single-line strings.
+ */
+Point Layouter::GetCharPosition(const char *ch) const
+{
+	/* Find the code point index which corresponds to the char
+	 * pointer into our UTF-8 source string. */
+	size_t index = 0;
+	const char *str = this->string;
+	while (str < ch) {
+		WChar c;
+		size_t len = Utf8Decode(&c, str);
+		if (c == '\0' || c == '\n') break;
+		str += len;
+#ifdef WITH_ICU
+		/* ICU uses UTF-16 internally which means we need to account for surrogate pairs. */
+		index += len < 4 ? 1 : 2;
+#else
+		index++;
+#endif
+	}
+
+	if (str == ch) {
+		/* Valid character. */
+		const ParagraphLayout::Line *line = *this->Begin();
+
+		/* Pointer to the end-of-string/line marker? Return total line width. */
+		if (*ch == '\0' || *ch == '\n') {
+			Point p = { line->getWidth(), 0 };
+			return p;
+		}
+
+		/* Scan all runs until we've found our code point index. */
+		for (int run_index = 0; run_index < line->countRuns(); run_index++) {
+			const ParagraphLayout::VisualRun *run = line->getVisualRun(run_index);
+
+			for (int i = 0; i < run->getGlyphCount(); i++) {
+				/* Matching glyph? Return position. */
+				if ((size_t)run->getGlyphToCharMap()[i] == index) {
+					Point p = { run->getPositions()[i * 2], run->getPositions()[i * 2 + 1] };
+					return p;
+				}
+			}
+		}
+	}
+
+	Point p = { 0, 0 };
+	return p;
+}
+
 /**
  * Get a static font instance.
  */

src/gfx_layout.h

@@ -168,6 +168,8 @@ class Layouter : public AutoDeleteSmallVector<ParagraphLayout::Line *, 4> {
 	typedef WChar CharType; ///< The type of character used within the layouter.
 #endif /* WITH_ICU */
 
+	const char *string; ///< Pointer to the original string.
+
 	size_t AppendToBuffer(CharType *buff, const CharType *buffer_last, WChar c);
 	ParagraphLayout *GetParagraphLayout(CharType *buff, CharType *buff_end, FontMap &fontMapping);
 
@@ -209,6 +211,7 @@ class Layouter : public AutoDeleteSmallVector<ParagraphLayout::Line *, 4> {
 public:
 	Layouter(const char *str, int maxw = INT32_MAX, TextColour colour = TC_FROMSTRING, FontSize fontsize = FS_NORMAL);
 	Dimension GetBounds();
+	Point GetCharPosition(const char *ch) const;
 
 	static void ResetFontCache(FontSize size);
 	static void ResetLineCache();

src/textbuf.cpp

@@ -81,18 +81,17 @@ void Textbuf::DelChar(bool backspace)
 	if (backspace) s = Utf8PrevChar(s);
 
 	uint16 len = (uint16)Utf8Decode(&c, s);
-	uint width = GetCharacterWidth(FS_NORMAL, c);
-
-	this->pixels -= width;
-	if (backspace) {
-		this->caretpos   -= len;
-		this->caretxoffs -= width;
-	}
 
 	/* Move the remaining characters over the marker */
 	memmove(s, s + len, this->bytes - (s - this->buf) - len);
 	this->bytes -= len;
 	this->chars--;
+
+	this->UpdateWidth();
+	if (backspace) {
+		this->caretpos -= len;
+		this->UpdateCaretPosition();
+	}
 }
 
 /**
@@ -159,17 +158,16 @@ void Textbuf::DeleteAll()
  */
 bool Textbuf::InsertChar(WChar key)
 {
-	const byte charwidth = GetCharacterWidth(FS_NORMAL, key);
 	uint16 len = (uint16)Utf8CharLen(key);
 	if (this->bytes + len <= this->max_bytes && this->chars + 1 <= this->max_chars) {
 		memmove(this->buf + this->caretpos + len, this->buf + this->caretpos, this->bytes - this->caretpos);
 		Utf8Encode(this->buf + this->caretpos, key);
 		this->chars++;
 		this->bytes  += len;
-		this->pixels += charwidth;
+		this->UpdateWidth();
 
 		this->caretpos   += len;
-		this->caretxoffs += charwidth;
+		this->UpdateCaretPosition();
 		return true;
 	}
 	return false;
@@ -187,7 +185,7 @@ bool Textbuf::InsertClipboard()
 
 	if (!GetClipboardContents(utf8_buf, lengthof(utf8_buf))) return false;
 
-	uint16 pixels = 0, bytes = 0, chars = 0;
+	uint16 bytes = 0, chars = 0;
 	WChar c;
 	for (const char *ptr = utf8_buf; (c = Utf8Consume(&ptr)) != '\0';) {
 		if (!IsValidChar(c, this->afilter)) break;
@@ -196,9 +194,6 @@ bool Textbuf::InsertClipboard()
 		if (this->bytes + bytes + len > this->max_bytes) break;
 		if (this->chars + chars + 1   > this->max_chars) break;
 
-		byte char_pixels = GetCharacterWidth(FS_NORMAL, c);
-
-		pixels += char_pixels;
 		bytes += len;
 		chars++;
 	}
@@ -207,8 +202,6 @@ bool Textbuf::InsertClipboard()
 
 	memmove(this->buf + this->caretpos + bytes, this->buf + this->caretpos, this->bytes - this->caretpos);
 	memcpy(this->buf + this->caretpos, utf8_buf, bytes);
-	this->pixels += pixels;
-	this->caretxoffs += pixels;
 
 	this->bytes += bytes;
 	this->chars += chars;
@@ -217,6 +210,9 @@ bool Textbuf::InsertClipboard()
 	assert(this->chars <= this->max_chars);
 	this->buf[this->bytes - 1] = '\0'; // terminating zero
 
+	this->UpdateWidth();
+	this->UpdateCaretPosition();
+
 	return true;
 }
 
@@ -242,7 +238,7 @@ WChar Textbuf::MoveCaretLeft()
 	const char *s = Utf8PrevChar(this->buf + this->caretpos);
 	Utf8Decode(&c, s);
 	this->caretpos    = s - this->buf;
-	this->caretxoffs -= GetCharacterWidth(FS_NORMAL, c);
+	this->UpdateCaretPosition();
 
 	return c;
 }
@@ -267,12 +263,24 @@ WChar Textbuf::MoveCaretRight()
 
 	WChar c;
 	this->caretpos   += (uint16)Utf8Decode(&c, this->buf + this->caretpos);
-	this->caretxoffs += GetCharacterWidth(FS_NORMAL, c);
+	this->UpdateCaretPosition();
 
 	Utf8Decode(&c, this->buf + this->caretpos);
 	return c;
 }
 
+/** Update pixel width of the text. */
+void Textbuf::UpdateWidth()
+{
+	this->pixels = GetStringBoundingBox(this->buf, FS_NORMAL).width;
+}
+
+/** Update pixel position of the caret. */
+void Textbuf::UpdateCaretPosition()
+{
+	this->caretxoffs = this->chars > 1 ? GetCharPosInString(this->buf, this->buf + this->caretpos, FS_NORMAL).x : 0;
+}
+
 /**
  * Handle text navigation with arrow keys left/right.
  * This defines where the caret will blink and the next character interaction will occur
@@ -336,12 +344,12 @@ bool Textbuf::MovePos(uint16 keycode)
 
 		case WKC_HOME:
 			this->caretpos = 0;
-			this->caretxoffs = 0;
+			this->UpdateCaretPosition();
 			return true;
 
 		case WKC_END:
 			this->caretpos = this->bytes - 1;
-			this->caretxoffs = this->pixels;
+			this->UpdateCaretPosition();
 			return true;
 
 		default:
@@ -418,21 +426,20 @@ void Textbuf::UpdateSize()
 {
 	const char *buf = this->buf;
 
-	this->pixels = 0;
 	this->chars = this->bytes = 1; // terminating zero
 
 	WChar c;
 	while ((c = Utf8Consume(&buf)) != '\0') {
-		this->pixels += GetCharacterWidth(FS_NORMAL, c);
 		this->bytes += Utf8CharLen(c);
 		this->chars++;
 	}
-
 	assert(this->bytes <= this->max_bytes);
 	assert(this->chars <= this->max_chars);
 
 	this->caretpos = this->bytes - 1;
-	this->caretxoffs = this->pixels;
+	this->UpdateWidth();
+
+	this->UpdateCaretPosition();
 }
 
 /**

src/textbuf_type.h

@@ -69,6 +69,8 @@ private:
 	bool CanMoveCaretRight();
 	WChar MoveCaretRight();
 
+	void UpdateWidth();
+	void UpdateCaretPosition();
 };
 
 #endif /* TEXTBUF_TYPE_H */