Add text components 021-040 with demos and behavior tests

pixel/canvas.go

@@ -221,6 +221,30 @@ func (g Canvas) Text(x, y int, s string, ink Slot, scale int) {
 	}
 }
 
+// TextBlend draws s, glyph dots dithered from top to bottom.
+func (g Canvas) TextBlend(x, y int, s string, top, bottom Slot, scale int) {
+	checkScale(scale)
+	span := LineHeight * scale
+	for _, r := range s {
+		gl := glyphOf(r)
+		gx := x + gl.x*scale
+		for j := range gl.h * scale {
+			yy := y + gl.top()*scale + j
+			level := min(16, (yy-y)*17/span)
+			row := bayer[(g.gy+yy)&3]
+			for _, part := range [2]struct {
+				s    Slot
+				down bool
+			}{{top, false}, {bottom, true}} {
+				runs(gl.w*scale, func(i int) bool {
+					return gl.on(i/scale, j/scale) && (row[(g.gx+gx+i)&3] < level) == part.down
+				}, func(a, b int) { g.Rect(gx+a, yy, b-a, 1, part.s) })
+			}
+		}
+		x += gl.adv * scale
+	}
+}
+
 // Micro draws s in the 3×5 micro font.
 func (g Canvas) Micro(x, y int, s string, ink Slot, scale int) {
 	checkScale(scale)

pixel/canvas_test.go

@@ -239,3 +239,32 @@ func TestTextAndMicroDraw(t *testing.T) {
 		}
 	}
 }
+
+func TestTextBlend(t *testing.T) {
+	plain := canvas(t, 40, 20, func(g pixel.Canvas) { g.Text(2, 2, "HM", pixel.Ink, 1) })
+	blend := canvas(t, 40, 20, func(g pixel.Canvas) { g.TextBlend(2, 2, "HM", pixel.Accent, pixel.Good, 1) })
+	tops, bottoms := 0, 0
+	for y := range 20 {
+		for x := range 40 {
+			ink, got := plain.at(x, y) == pixel.Ink, blend.at(x, y)
+			if ink != (got == pixel.Accent || got == pixel.Good) {
+				t.Fatalf("dot %d,%d: text %v, blend %v", x, y, ink, got)
+			}
+			if got == pixel.Accent && y > 2+pixel.LineHeight*3/4 || got == pixel.Good && y < 2+pixel.LineHeight/4 {
+				t.Fatalf("dot %d,%d has %v on the wrong end", x, y, got)
+			}
+			tops += boolInt(got == pixel.Accent)
+			bottoms += boolInt(got == pixel.Good)
+		}
+	}
+	if tops == 0 || bottoms == 0 {
+		t.Fatalf("blend used %d top and %d bottom dots", tops, bottoms)
+	}
+}
+
+func boolInt(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}

pixel/element.go

@@ -25,7 +25,7 @@ func Text(c *ui.Context, s string, o TextOptions) *ui.Element {
 	if o.Wrap {
 		width, check = WrapWidth(c, e)
 	}
-	lines := textLines(s, width/scale, o.MaxLines)
+	lines := Wrap(s, width/scale, o.MaxLines)
 	if o.Wrap {
 		e.Height(k.D(len(lines) * LineHeight * scale))
 	} else {
@@ -44,8 +44,8 @@ func Text(c *ui.Context, s string, o TextOptions) *ui.Element {
 	})
 }
 
-// textLines wraps s, cutting to maxLines with an ellipsis.
-func textLines(s string, width, maxLines int) []string {
+// Wrap wraps s to width; past maxLines, an ellipsis.
+func Wrap(s string, width, maxLines int) []string {
 	if maxLines < 0 {
 		panic(fmt.Sprintf("pixel: MaxLines %d", maxLines))
 	}

pixel/engine_internal_test.go

@@ -24,7 +24,7 @@ func TestRuns(t *testing.T) {
 	}
 }
 
-func TestTextLinesEllipsis(t *testing.T) {
+func TestWrapEllipsis(t *testing.T) {
 	cases := []struct {
 		s        string
 		width, n int
@@ -37,8 +37,8 @@ func TestTextLinesEllipsis(t *testing.T) {
 		{"像素风格组件库", 36, 2, []string{"像素风", "格组…"}},
 	}
 	for _, c := range cases {
-		if got := textLines(c.s, c.width, c.n); !slices.Equal(got, c.want) {
-			t.Errorf("textLines(%q, %d, %d) = %q, want %q", c.s, c.width, c.n, got, c.want)
+		if got := Wrap(c.s, c.width, c.n); !slices.Equal(got, c.want) {
+			t.Errorf("Wrap(%q, %d, %d) = %q, want %q", c.s, c.width, c.n, got, c.want)
 		}
 	}
 }