From 26676f385c051affd123a40c5e354a52e64e8fc2 Mon Sep 17 00:00:00 2001
From: Vsevolod Stakhov <vsevolod@highsecure.ru>
Date: Mon, 14 Jun 2021 13:42:28 +0100
Subject: [PATCH] [Project] Html/Css: Implement visibility rules for a block

---
 src/libserver/html/html.cxx       |  2 ++
 src/libserver/html/html_block.hxx | 55 +++++++++++++++++++++++++++++++
 src/lua/lua_html.cxx              |  3 +-
 3 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/src/libserver/html/html.cxx b/src/libserver/html/html.cxx
index eb4d806d7..f30b9d1b8 100644
--- a/src/libserver/html/html.cxx
+++ b/src/libserver/html/html.cxx
@@ -1654,6 +1654,8 @@ html_process_input(rspamd_mempool_t *pool,
 	/* Propagate styles */
 	hc->traverse_block_tags([](const html_tag *tag) -> bool {
 		if (tag->block) {
+			tag->block->compute_visibility();
+
 			for (const auto *cld_tag : tag->children) {
 				if (cld_tag->block) {
 					cld_tag->block->propagate_block(*tag->block);
diff --git a/src/libserver/html/html_block.hxx b/src/libserver/html/html_block.hxx
index 913480864..0958debdd 100644
--- a/src/libserver/html/html_block.hxx
+++ b/src/libserver/html/html_block.hxx
@@ -18,6 +18,7 @@
 #pragma once
 
 #include "libserver/css/css_value.hxx"
+#include <cmath>
 
 namespace rspamd::html {
 
@@ -39,6 +40,7 @@ struct html_block {
 	constexpr static const auto width_mask = 0x1 << 3;
 	constexpr static const auto display_mask = 0x1 << 4;
 	constexpr static const auto font_size_mask = 0x1 << 5;
+	constexpr static const auto invisible_flag = 0x1 << 6;
 
 	/* Helpers to set mask when setting the elements */
 	auto set_fgcolor(const rspamd::css::css_color &c) -> void {
@@ -159,6 +161,59 @@ struct html_block {
 		size_prop(font_size_mask, font_size, other.font_size, 1024);
 	}
 
+	auto compute_visibility(void) -> void {
+		if (mask & display_mask) {
+			if (display == css::css_display_value::DISPLAY_HIDDEN) {
+				mask |= invisible_flag;
+
+				return;
+			}
+		}
+
+		if (mask & font_size_mask) {
+			if (font_size == 0) {
+				mask |= invisible_flag;
+
+				return;
+			}
+		}
+
+		/* Check if we have both bg/fg colors */
+		if ((mask & (bg_color_mask|fg_color_mask)) == (bg_color_mask|fg_color_mask)) {
+			if (fg_color.alpha < 10) {
+				/* Too transparent */
+				mask |= invisible_flag;
+
+				return;
+			}
+
+			if (bg_color.alpha > 10) {
+				auto diff_r = std::abs(fg_color.r - bg_color.r);
+				auto diff_g = std::abs(fg_color.g - bg_color.g);
+				auto diff_b = std::abs(fg_color.b - bg_color.b);
+				auto ravg = (fg_color.r + bg_color.r) / 2.0;
+
+				diff_r *= diff_r;
+				diff_g *= diff_g;
+				diff_b *= diff_b;
+
+				auto diff = std::sqrt(2.0 * diff_r + 4.0 * diff_g + 3.0 * diff_b +
+						  (ravg * (diff_r - diff_b) / 256.0)) / 256.0;
+
+				if (diff < 0.1) {
+					mask |= invisible_flag;
+					return;
+				}
+			}
+		}
+
+		mask &= ~invisible_flag;
+	}
+
+	auto is_visible(void) const -> bool {
+		return (mask & invisible_flag) != 0;
+	}
+
 	/**
 	 * Returns a default html block for root HTML element
 	 * @return
diff --git a/src/lua/lua_html.cxx b/src/lua/lua_html.cxx
index 3b9b7a7de..0972fde98 100644
--- a/src/lua/lua_html.cxx
+++ b/src/lua/lua_html.cxx
@@ -381,9 +381,8 @@ lua_html_push_block (lua_State *L, const struct rspamd::html::html_block *bl)
 		lua_settable(L, -3);
 	}
 
-	/* TODO: fix */
 	lua_pushstring(L, "visible");
-	lua_pushboolean(L, true);
+	lua_pushboolean(L, (bl->mask & rspamd::html::html_block::invisible_flag) == 0);
 	lua_settable(L, -3);
 }
 
-- 
2.39.5