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text: [API] be absolutely consistent about newline truncation

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This commit changes the shaper's behavior when truncating text. Previously, if the final
line allowed by MaxLines ended with a newline, whether or not that newline was truncated
depended upon whether we knew that there was more text after the current paragraph. However,
this makes reasoning about what the shaper will do quite difficult. It seems better to be
consistent. Now we will insert a truncator at the end of the final line if it has a trailing
newline character, regardless of whether it ends the input text.

Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit is contained in:
Chris Waldon
2023-08-22 16:23:02 -04:00
committed by Elias Naur
parent 83202263b9
commit 8679f49fff
2 changed files with 100 additions and 63 deletions
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text/shaper_test.go
+36 -16
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@@ -154,9 +154,11 @@ func TestWrappingForcedTruncation(t *testing.T) {
// consistently and does not create spurious lines of text.
func TestShapingNewlineHandling(t *testing.T) {
type testcase struct {
textInput string
expectedLines int
expectedGlyphs int
textInput string
expectedLines int
expectedGlyphs int
maxLines int
expectedTruncated int
}
for _, tc := range []testcase{
{textInput: "a\n", expectedLines: 1, expectedGlyphs: 3},
@@ -165,21 +167,41 @@ func TestShapingNewlineHandling(t *testing.T) {
{textInput: "\n", expectedLines: 1, expectedGlyphs: 2},
{textInput: "\n\n", expectedLines: 2, expectedGlyphs: 3},
{textInput: "\n\n\n", expectedLines: 3, expectedGlyphs: 4},
{textInput: "\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 1, expectedTruncated: 1},
{textInput: "\n\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 1, expectedTruncated: 2},
{textInput: "\n\n\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 1, expectedTruncated: 3},
{textInput: "a\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 2, expectedTruncated: 1},
{textInput: "a\n\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 2, expectedTruncated: 2},
{textInput: "a\n\n\n", expectedLines: 1, maxLines: 1, expectedGlyphs: 2, expectedTruncated: 3},
{textInput: "\n", expectedLines: 1, maxLines: 2, expectedGlyphs: 2},
{textInput: "\n\n", expectedLines: 2, maxLines: 2, expectedGlyphs: 2, expectedTruncated: 1},
{textInput: "\n\n\n", expectedLines: 2, maxLines: 2, expectedGlyphs: 2, expectedTruncated: 2},
{textInput: "a\n", expectedLines: 1, maxLines: 2, expectedGlyphs: 3},
{textInput: "a\n\n", expectedLines: 2, maxLines: 2, expectedGlyphs: 3, expectedTruncated: 1},
{textInput: "a\n\n\n", expectedLines: 2, maxLines: 2, expectedGlyphs: 3, expectedTruncated: 2},
} {
t.Run(fmt.Sprintf("%q", tc.textInput), func(t *testing.T) {
t.Run(fmt.Sprintf("%q-maxLines%d", tc.textInput, tc.maxLines), func(t *testing.T) {
ltrFace, _ := opentype.Parse(goregular.TTF)
collection := []FontFace{{Face: ltrFace}}
cache := NewShaper(NoSystemFonts(), WithCollection(collection))
checkGlyphs := func() {
glyphs := []Glyph{}
runes := 0
truncated := 0
for g, ok := cache.NextGlyph(); ok; g, ok = cache.NextGlyph() {
glyphs = append(glyphs, g)
runes += g.Runes
if g.Flags&FlagTruncator == 0 {
runes += g.Runes
} else {
truncated += g.Runes
}
}
if expected := len([]rune(tc.textInput)); expected != runes {
if expected := len([]rune(tc.textInput)) - tc.expectedTruncated; expected != runes {
t.Errorf("expected %d runes, got %d", expected, runes)
}
if truncated != tc.expectedTruncated {
t.Errorf("expected %d truncated runes, got %d", tc.expectedTruncated, truncated)
}
if len(glyphs) != tc.expectedGlyphs {
t.Errorf("expected %d glyphs, got %d", tc.expectedGlyphs, len(glyphs))
}
@@ -207,29 +229,27 @@ func TestShapingNewlineHandling(t *testing.T) {
t.Errorf("expected paragraph start glyph to have cursor y")
}
}
if count := strings.Count(tc.textInput, "\n"); found != count {
if count := strings.Count(tc.textInput, "\n"); found != count && tc.maxLines == 0 {
t.Errorf("expected %d paragraph breaks, found %d", count, found)
} else if tc.maxLines > 0 && found > tc.maxLines {
t.Errorf("expected %d paragraph breaks due to truncation, found %d", tc.maxLines, found)
}
}
cache.LayoutString(Parameters{
params := Parameters{
Alignment: Middle,
PxPerEm: fixed.I(10),
MinWidth: 200,
MaxWidth: 200,
Locale: english,
}, tc.textInput)
MaxLines: tc.maxLines,
}
cache.LayoutString(params, tc.textInput)
if lineCount := len(cache.txt.lines); lineCount > tc.expectedLines {
t.Errorf("shaping string %q created %d lines", tc.textInput, lineCount)
}
checkGlyphs()
cache.Layout(Parameters{
Alignment: Middle,
PxPerEm: fixed.I(10),
MinWidth: 200,
MaxWidth: 200,
Locale: english,
}, strings.NewReader(tc.textInput))
cache.Layout(params, strings.NewReader(tc.textInput))
if lineCount := len(cache.txt.lines); lineCount > tc.expectedLines {
t.Errorf("shaping reader %q created %d lines", tc.textInput, lineCount)
}