From 24500f52a3bdbe9a2a033dcaa300c54ae3321720 Mon Sep 17 00:00:00 2001
From: Alec Murphy <alec@checksum.fail>
Date: Wed, 16 Apr 2025 14:53:16 -0400
Subject: [PATCH] System/Libraries/(Css,Graphics2D,Html): Support underlined
 text

This commit adds the necessary functions to minimally implement support
for CSS text-decoration: underline.
---
 System/Libraries/Css/Tokenizer.HC  |  2 ++
 System/Libraries/Graphics2D.HC     | 38 ++++++++++++++++++++++++++++++
 System/Libraries/Html/Renderer.HC  | 23 ++++++++++++++++++
 System/Libraries/Html/Tokenizer.HC |  1 +
 4 files changed, 64 insertions(+)

diff --git a/System/Libraries/Css/Tokenizer.HC b/System/Libraries/Css/Tokenizer.HC
index 6bf157b..707acc3 100644
--- a/System/Libraries/Css/Tokenizer.HC
+++ b/System/Libraries/Css/Tokenizer.HC
@@ -1,6 +1,8 @@
 #define CSS_TEXT_ALIGN_CENTER 1
 #define CSS_TEXT_ALIGN_RIGHT 2
 
+#define CSS_TEXT_UNDERLINE 1
+
 #define CSS_TOKENIZER_STATE_CONSUME_MATCH 0
 #define CSS_TOKENIZER_STATE_CONSUME_PROPERTY 1
 #define CSS_TOKENIZER_STATE_CONSUME_VALUE 2
diff --git a/System/Libraries/Graphics2D.HC b/System/Libraries/Graphics2D.HC
index 9681345..655b79f 100644
--- a/System/Libraries/Graphics2D.HC
+++ b/System/Libraries/Graphics2D.HC
@@ -1162,6 +1162,24 @@ I64 X2Pos(CDC* src)
     return -1;
 }
 
+I64 Y2Pos(CDC* src)
+{
+    I64 x = src->width - 1;
+    I64 y = src->height - 1;
+    I64 color;
+    while (y > -1) {
+        x = src->width - 1;
+        while (x > -1) {
+            color = GrPeek(src, x, y);
+            if (color)
+                return y;
+            x--;
+        }
+        y--;
+    }
+    return -1;
+}
+
 I64 @get_truetype_text_width(U8* font_name, I64 size, U8* text)
 {
     stbtt_fontinfo* font = Fonts->@(font_name);
@@ -1178,6 +1196,26 @@ I64 @get_truetype_text_width(U8* font_name, I64 size, U8* text)
     return res;
 }
 
+I64 @get_truetype_baseline(U8* font_name, I64 size)
+{
+    stbtt_fontinfo* font = Fonts->@(font_name);
+    if (!font) {
+        return 0;
+    }
+    I64 res = 0;
+    CDC* dc = DCNew(Display.Width() / 2, (size * 2));
+    Free(dc->body);
+    I32 i32char[16];
+    MemSet(&i32char, NULL, 16);
+    i32char[0] = 'o';
+    dc->body = @stbtt_RenderText(font, dc->width_internal, dc->height, ToI64(size * 1.2), &i32char);
+    dc->width -= 16;
+    dc->height -= size / 4;
+    res = Y2Pos(dc);
+    DCDel(dc);
+    return res;
+}
+
 U0 Text2D(Context2D* ctx, U8* font_name, I64 x, I64 y, I64 size, U32 color, U8* text)
 {
     stbtt_fontinfo* font = Fonts->@(font_name);
diff --git a/System/Libraries/Html/Renderer.HC b/System/Libraries/Html/Renderer.HC
index 9045727..34bca8e 100644
--- a/System/Libraries/Html/Renderer.HC
+++ b/System/Libraries/Html/Renderer.HC
@@ -308,6 +308,7 @@ Bool @apply_css_rules_to_node(@html_dom_node* node, HtmlRenderer* renderer)
         node->fontSize = node->parentNode->fontSize;
         node->fontWeight = node->parentNode->fontWeight;
         node->textAlign = node->parentNode->textAlign;
+        node->textDecoration = node->parentNode->textDecoration;
         node->italic = node->parentNode->italic;
     }
 
@@ -425,6 +426,15 @@ Bool @apply_css_rules_to_node(@html_dom_node* node, HtmlRenderer* renderer)
                     if (!StrICmp(key->name, "text-align") && !StrICmp(values->@(0), "right"))
                         node->textAlign = CSS_TEXT_ALIGN_RIGHT;
 
+                    if (!StrICmp(key->name, "text-decoration")) {
+                        if (!StrICmp(values->@(0), "none")) {
+                            node->textDecoration = 0;
+                        }
+                        if (!StrICmp(values->@(0), "underline")) {
+                            node->textDecoration = CSS_TEXT_UNDERLINE;
+                        }
+                    }
+
                     if (!StrICmp(key->name, "line-height") && !StrICmp(values->@(0) + StrLen(values->@(0)) - 2, "px")) {
                         StrCpy(node_tmpnum_buf, values->@(0));
                         node_tmpnum_buf[StrLen(node_tmpnum_buf) - 2] = NULL;
@@ -849,6 +859,7 @@ U0 @render_node_text(@html_dom_node* node, HtmlRenderer* renderer)
 
     U32 fragment_bounding_box_color = Color(0x00, 0xff, 0x00);
     U8* font_name = @resolved_font_name_for_node(node->parentNode);
+    I64 underline_y_pos = -1;
 
     for (i = 0; i < fragment_count; i++) {
         if (fragments[i] && *fragments[i]) {
@@ -860,6 +871,18 @@ U0 @render_node_text(@html_dom_node* node, HtmlRenderer* renderer)
                 fragment_widget->data = node;
                 fragment_widget->ctx = NewContext2D(text_width, ToI64(node->parentNode->fontSize * 1.2))->fill(node->parentNode->backgroundColor)->text(font_name, 0, 0, node->parentNode->fontSize, node->parentNode->color, fragments[i]);
 
+                switch (node->parentNode->textDecoration) {
+                case CSS_TEXT_UNDERLINE:
+                    if (underline_y_pos < 0)
+                        underline_y_pos = @get_truetype_baseline(font_name, node->parentNode->fontSize) + 2;
+                    if (!(underline_y_pos < 0)) {
+                        fragment_widget->ctx->line(0, underline_y_pos, fragment_widget->ctx->width, underline_y_pos, node->parentNode->color);
+                    }
+                    break;
+                default:
+                    break;
+                }
+
                 if (renderer->debug && fragment_widget->ctx) {
                     fragment_widget->ctx->line(0, 0, fragment_widget->ctx->width - 1, 0, fragment_bounding_box_color);
                     fragment_widget->ctx->line(0, fragment_widget->ctx->height - 1, fragment_widget->ctx->width - 1, fragment_widget->ctx->height - 1, fragment_bounding_box_color);
diff --git a/System/Libraries/Html/Tokenizer.HC b/System/Libraries/Html/Tokenizer.HC
index 39ee371..99d6fdf 100644
--- a/System/Libraries/Html/Tokenizer.HC
+++ b/System/Libraries/Html/Tokenizer.HC
@@ -97,6 +97,7 @@ class @html_dom_node : JsonElement
     U8* fontFamily;
     I64 fontSize;
     I64 fontWeight;
+    I64 textDecoration;
     Bool italic;
     Bool display_block;
 };