Added a test for making uiDrawTextLayouts on empty strings. We're already off to a good start since we have a ~0 error on OS X...

examples/CMakeLists.txt

@@ -34,6 +34,7 @@ endif()
 _add_example(drawtext
 	drawtext/attributes.c
 	drawtext/basic.c
+	drawtext/emptystr_hittest.c
 	drawtext/hittest.c
 	drawtext/main.c
 	${_EXAMPLE_RESOURCES_RC}

examples/drawtext/drawtext.h

@@ -23,3 +23,6 @@ extern struct example *mkHitTestExample(void);
 
 // attributes.c
 extern struct example *mkAttributesExample(void);
+
+// emptystr_hittest.c
+extern struct example *mkEmptyStringExample(void);

examples/drawtext/emptystr_hittest.c

@@ -0,0 +1,254 @@
+// 20 january 2017
+#include "drawtext.h"
+
+// TODO FOR THIS FILE
+// get rid of it once we rewrite this example (which requires having more fine-grained scrolling control)
+
+// TODO double-check ligatures on all platforms to make sure we can place the cursor at the right place
+// TODO the hiding and showing does not work properly on GTK+
+// TODO using the arrow keys allows us to walk back to the end of the line on some platforms (TODO which?); IIRC arrow keys shouldn't do that
+// TODO make sure to check the cursor positions of RTL on all platforms
+
+static const char *text = "";
+static char fontFamily[] = "Helvetica";
+static uiDrawFontDescriptor defaultFont = {
+	.Family = fontFamily,
+	.Size = 14,
+	.Weight = uiDrawTextWeightNormal,
+	.Italic = uiDrawTextItalicNormal,
+	.Stretch = uiDrawTextStretchNormal,
+};
+static uiAttributedString *attrstr;
+static uiDrawTextLayoutParams params;
+
+#define margins 10
+
+static uiBox *panel;
+static uiBox *vbox;
+static uiLabel *caretLabel;
+static uiCheckbox *showLineBounds;
+static uiFontButton *fontButton;
+static uiCombobox *textAlign;
+
+static int caretLine = -1;
+static size_t caretPos;
+
+// TODO should be const?
+static uiDrawBrush fillBrushes[4] = {
+	{
+		.Type = uiDrawBrushTypeSolid,
+		.R = 1.0,
+		.G = 0.0,
+		.B = 0.0,
+		.A = 0.5,
+	},
+	{
+		.Type = uiDrawBrushTypeSolid,
+		.R = 0.0,
+		.G = 1.0,
+		.B = 0.0,
+		.A = 0.5,
+	},
+	{
+		.Type = uiDrawBrushTypeSolid,
+		.R = 0.0,
+		.G = 0.0,
+		.B = 1.0,
+		.A = 0.5,
+	},
+	{
+		.Type = uiDrawBrushTypeSolid,
+		.R = 0.0,
+		.G = 1.0,
+		.B = 1.0,
+		.A = 0.5,
+	},
+};
+
+static void draw(uiAreaDrawParams *p)
+{
+	uiDrawPath *path;
+	uiDrawTextLayout *layout;
+	uiDrawTextLayoutLineMetrics m;
+
+	// only clip the text, not the guides
+	uiDrawSave(p->Context);
+
+	path = uiDrawNewPath(uiDrawFillModeWinding);
+	uiDrawPathAddRectangle(path, margins, margins,
+		p->AreaWidth - 2 * margins,
+		p->AreaHeight - 2 * margins);
+	uiDrawPathEnd(path);
+	uiDrawClip(p->Context, path);
+	uiDrawFreePath(path);
+
+	params.Width = p->AreaWidth - 2 * margins;
+	layout = uiDrawNewTextLayout(&params);
+	uiDrawText(p->Context, layout, margins, margins);
+
+	uiDrawRestore(p->Context);
+
+	if (caretLine == -1) {
+		caretLine = uiDrawTextLayoutNumLines(layout) - 1;
+		caretPos = uiAttributedStringLen(attrstr);
+	}
+	uiDrawCaret(p->Context, margins, margins,
+		layout, caretPos, &caretLine);
+
+	if (uiCheckboxChecked(showLineBounds)) {
+		int i, n;
+		int fill = 0;
+
+		n = uiDrawTextLayoutNumLines(layout);
+		for (i = 0; i < n; i++) {
+			uiDrawTextLayoutLineGetMetrics(layout, i, &m);
+			path = uiDrawNewPath(uiDrawFillModeWinding);
+			uiDrawPathAddRectangle(path, margins + m.X, margins + m.Y,
+				m.Width, m.Height);
+			uiDrawPathEnd(path);
+			uiDrawFill(p->Context, path, fillBrushes + fill);
+			uiDrawFreePath(path);
+			fill = (fill + 1) % 4;
+		}
+	}
+
+	uiDrawFreeTextLayout(layout);
+}
+
+static void mouse(uiAreaMouseEvent *e)
+{
+	uiDrawTextLayout *layout;
+	char labelText[128];
+
+	if (e->Down != 1)
+		return;
+
+	params.Width = e->AreaWidth - 2 * margins;
+	layout = uiDrawNewTextLayout(&params);
+	uiDrawTextLayoutHitTest(layout,
+		e->X - margins, e->Y - margins,
+		&caretPos, &caretLine);
+	uiDrawFreeTextLayout(layout);
+
+	// TODO move this into the draw handler so it is reflected by keyboard-based position changes
+	// urgh %zd is not supported by MSVC with sprintf()
+	// TODO get that part in test/ about having no other option
+	sprintf(labelText, "pos %d line %d",
+		(int) caretPos, caretLine);
+	uiLabelSetText(caretLabel, labelText);
+
+	redraw();
+}
+
+static int key(uiAreaKeyEvent *e)
+{
+	size_t grapheme;
+
+	if (e->Up)
+		return 0;
+	if (e->Key != 0)
+		return 0;
+	switch (e->ExtKey) {
+	case uiExtKeyUp:
+		// TODO
+		return 1;
+	case uiExtKeyDown:
+		// TODO
+		return 1;
+	case uiExtKeyLeft:
+		grapheme = uiAttributedStringByteIndexToGrapheme(attrstr, caretPos);
+		if (grapheme == 0)
+			return 0;
+		grapheme--;
+		caretPos = uiAttributedStringGraphemeToByteIndex(attrstr, grapheme);
+		redraw();
+		return 1;
+	case uiExtKeyRight:
+		grapheme = uiAttributedStringByteIndexToGrapheme(attrstr, caretPos);
+		if (grapheme == uiAttributedStringNumGraphemes(attrstr))
+			return 0;
+		grapheme++;
+		caretPos = uiAttributedStringGraphemeToByteIndex(attrstr, grapheme);
+		redraw();
+		return 1;
+	}
+	return 0;
+}
+
+static struct example hitTestExample;
+
+// TODO share?
+static void checkboxChecked(uiCheckbox *c, void *data)
+{
+	redraw();
+}
+
+static void changeFont(uiFontButton *b, void *data)
+{
+	if (defaultFont.Family != fontFamily)
+		uiFreeText(defaultFont.Family);
+	// TODO rename defaultFont
+	uiFontButtonFont(fontButton, &defaultFont);
+	printf("{\n\tfamily: %s\n\tsize: %g\n\tweight: %d\n\titalic: %d\n\tstretch: %d\n}\n",
+		defaultFont.Family,
+		defaultFont.Size,
+		(int) (defaultFont.Weight),
+		(int) (defaultFont.Italic),
+		(int) (defaultFont.Stretch));
+	redraw();
+}
+
+static void changeTextAlign(uiCombobox *c, void *data)
+{
+	// note the order of the items added below
+	params.Align = (uiDrawTextLayoutAlign) uiComboboxSelected(textAlign);
+	redraw();
+}
+
+// TODO share?
+static uiCheckbox *newCheckbox(uiBox *box, const char *text)
+{
+	uiCheckbox *c;
+
+	c = uiNewCheckbox(text);
+	uiCheckboxOnToggled(c, checkboxChecked, NULL);
+	uiBoxAppend(box, uiControl(c), 0);
+	return c;
+}
+
+struct example *mkEmptyStringExample(void)
+{
+	panel = uiNewHorizontalBox();
+	vbox = uiNewVerticalBox();
+	// TODO the second vbox causes this not to stretch at least on OS X
+	uiBoxAppend(panel, uiControl(vbox), 1);
+	caretLabel = uiNewLabel("Caret information is shown here");
+	uiBoxAppend(vbox, uiControl(caretLabel), 0);
+	showLineBounds = newCheckbox(vbox, "Show Line Bounds (for debugging metrics)");
+	vbox = uiNewVerticalBox();
+	uiBoxAppend(panel, uiControl(vbox), 0);
+	fontButton = uiNewFontButton();
+	uiFontButtonOnChanged(fontButton, changeFont, NULL);
+	// TODO set the font button to the current defaultFont
+	uiBoxAppend(vbox, uiControl(fontButton), 0);
+	textAlign = uiNewCombobox();
+	// note that these are in the order in the enum
+	uiComboboxAppend(textAlign, "Left");
+	uiComboboxAppend(textAlign, "Center");
+	uiComboboxAppend(textAlign, "Right");
+	uiComboboxOnSelected(textAlign, changeTextAlign, NULL);
+	uiBoxAppend(vbox, uiControl(textAlign), 0);
+
+	hitTestExample.name = "Empty String";
+	hitTestExample.panel = uiControl(panel);
+	hitTestExample.draw = draw;
+	hitTestExample.mouse = mouse;
+	hitTestExample.key = key;
+
+	attrstr = uiNewAttributedString(text);
+	params.String = attrstr;
+	params.DefaultFont = &defaultFont;
+	params.Align = uiDrawTextLayoutAlignLeft;
+
+	return &hitTestExample;
+}

examples/drawtext/main.c

@@ -115,6 +115,11 @@ int main(void)
 	uiControlHide(examples[n]->panel);
 	uiBoxAppend(box, examples[n]->panel, 0);
 	n++;
+	examples[n] = mkEmptyStringExample();
+	uiComboboxAppend(exampleList, examples[n]->name);
+	uiControlHide(examples[n]->panel);
+	uiBoxAppend(box, examples[n]->panel, 0);
+	n++;
 	// and set things up for the initial state
 	uiComboboxSetSelected(exampleList, 0);
 	uiComboboxOnSelected(exampleList, onExampleChanged, NULL);