From 37554dd719034b911f15bd0b1c4bcacccdc9b647 Mon Sep 17 00:00:00 2001
From: Sasha Koshka <sashakoshka@tebibyte.media>
Date: Tue, 10 Sep 2024 11:20:08 -0400
Subject: [PATCH] Add measurement stage

---
 measure.go      | 45 +++++++++++++++++++++++++++++++
 measure_test.go | 70 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 measure.go
 create mode 100644 measure_test.go

diff --git a/measure.go b/measure.go
new file mode 100644
index 0000000..89345e6
--- /dev/null
+++ b/measure.go
@@ -0,0 +1,45 @@
+package typeset
+
+import "golang.org/x/image/font"
+import "golang.org/x/image/math/fixed"
+
+func measure (tokens []token, face font.Face) {
+	var lastRune rune
+	for index, token := range tokens {
+		var x fixed.Int26_6
+		for index, runl := range token.runes {
+			advance, ok := face.GlyphAdvance(runl.run)
+			if !ok { advance = tofuAdvance(face) }
+			advance += face.Kern(lastRune, runl.run)
+			
+			runl.x = x
+			x += advance
+			lastRune = runl.run
+			token.runes[index] = runl
+		}
+		token.width = x
+		tokens[index] = token
+	}
+}
+
+const tofuStandinRune     = 'M'
+const fallbackTofuAdvance = 16
+const fallbackTofuWidth   = 14
+const fallbackTofuAscend  = 16
+
+func tofuAdvance (face font.Face) fixed.Int26_6 {
+	if advance, ok := face.GlyphAdvance(tofuStandinRune); ok {
+		return advance
+	} else {
+		return fallbackTofuAdvance
+	}
+}
+
+func tofuBounds (face font.Face) (fixed.Rectangle26_6, fixed.Int26_6) {
+	if bounds, advance, ok := face.GlyphBounds(tofuStandinRune); ok {
+		return bounds, advance
+	} else {
+		return fixed.R(0, -fallbackTofuAscend, fallbackTofuWidth, 0),
+			fallbackTofuAdvance
+	}
+}
diff --git a/measure_test.go b/measure_test.go
new file mode 100644
index 0000000..99d00be
--- /dev/null
+++ b/measure_test.go
@@ -0,0 +1,70 @@
+package typeset
+
+import "testing"
+import "golang.org/x/image/math/fixed"
+import "golang.org/x/image/font/basicfont"
+
+const basicfontFace7x13advance = 7
+
+func tkw (kind tokenKind, value string, width fixed.Int26_6) token {
+	tok := tk(kind, value)
+	tok.width = width
+	for index, runl := range tok.runes {
+		runl.x = fixed.I(basicfontFace7x13advance * index)
+		tok.runes[index] = runl
+	}
+	return tok
+}
+
+func TestMeasure (test *testing.T) {
+	// ---- processing ----
+	tokens := []token {
+		tk(tokenKindWord, "hello"),
+		tk(tokenKindSpace, " "),
+		tk(tokenKindWord, "\rworld!"),
+		tk(tokenKindLineBreak, "\n"),
+		tk(tokenKindWord, "foo"),
+		tk(tokenKindLineBreak, "\n"),
+		tk(tokenKindLineBreak, "\r\n"),
+		tk(tokenKindWord, "bar"),
+		tk(tokenKindTab, "\t"),
+		tk(tokenKindWord, "baz"),
+		tk(tokenKindTab, "\t\t"),
+		tk(tokenKindWord, "something"),
+	}
+	measure(tokens, basicfont.Face7x13)
+	
+	// ---- correct data ----
+	correctTokens := []token {
+		tkw(tokenKindWord,      "hello",     fixed.I(35)),
+		tkw(tokenKindSpace,     " ",         fixed.I( 7)),
+		tkw(tokenKindWord,      "\rworld!",  fixed.I(49)),
+		tkw(tokenKindLineBreak, "\n",        fixed.I( 7)),
+		tkw(tokenKindWord,      "foo",       fixed.I(21)),
+		tkw(tokenKindLineBreak, "\n",        fixed.I( 7)),
+		tkw(tokenKindLineBreak, "\r\n",      fixed.I(14)),
+		tkw(tokenKindWord,      "bar",       fixed.I(21)),
+		tkw(tokenKindTab,       "\t",        fixed.I( 7)),
+		tkw(tokenKindWord,      "baz",       fixed.I(21)),
+		tkw(tokenKindTab,       "\t\t",      fixed.I(14)),
+		tkw(tokenKindWord,      "something", fixed.I(63)),
+	}
+
+	// ---- testing ----
+	if len(tokens) != len(correctTokens) {
+		test.Logf("len(tokens) != len(correctTokens): %d, %d", len(tokens), len(correctTokens))
+		test.Log("GOT")
+		logTokens(test, tokens)
+		test.Log("CORRECT")
+		logTokens(test, correctTokens)
+		test.FailNow()
+	}
+	if !compareTokens(tokens, correctTokens) {
+		test.Log("tokens != correctTokens:")
+		test.Log("GOT")
+		logTokens(test, tokens)
+		test.Log("CORRECT")
+		logTokens(test, correctTokens)
+		test.FailNow()
+	}
+}