From 3a874f1ea6d1fcfdfb2c8d04343a38365603a55e Mon Sep 17 00:00:00 2001
From: ohyzha <oleksii.hyzha.ext@madvoxel.com>
Date: Thu, 23 Jan 2025 13:21:02 +0200
Subject: [PATCH] reduce spacing between multiple lines

---
 examples/ExampleApps/TextExampleApp.cpp |  4 +-
 openVulkanoCpp/Scene/TextDrawable.cpp   | 73 +++++++++++++++++++++++--
 openVulkanoCpp/Scene/TextDrawable.hpp   |  2 +
 3 files changed, 74 insertions(+), 5 deletions(-)

diff --git a/examples/ExampleApps/TextExampleApp.cpp b/examples/ExampleApps/TextExampleApp.cpp
index 0e76db8..0558dc4 100644
--- a/examples/ExampleApps/TextExampleApp.cpp
+++ b/examples/ExampleApps/TextExampleApp.cpp
@@ -108,7 +108,9 @@ namespace OpenVulkano
 					}
 					else if (i == 1)
 					{
-						t = new TextDrawable(msdfMetadataInfo, texts[j].second);
+						TextConfig cfg = texts[j].second;
+						cfg.minimalSpacingBetweenMultipleLines = false;
+						t = new TextDrawable(msdfMetadataInfo, cfg);
 					}
 					else if (i == 2)
 					{
diff --git a/openVulkanoCpp/Scene/TextDrawable.cpp b/openVulkanoCpp/Scene/TextDrawable.cpp
index a140294..0181f6a 100644
--- a/openVulkanoCpp/Scene/TextDrawable.cpp
+++ b/openVulkanoCpp/Scene/TextDrawable.cpp
@@ -79,6 +79,55 @@ namespace OpenVulkano::Scene
 		return m_atlasData->GetGlyphs().begin()->first;
 	}
 
+	std::vector<float> TextDrawable::GetHeightsBetweenLines(const std::string& text) const
+	{
+		if (!m_cfg.minimalSpacingBetweenMultipleLines)
+		{
+			return {};
+		}
+		const std::map<uint32_t, GlyphInfo>& symbols = m_atlasData->GetGlyphs();
+		const uint32_t fallbackGlyph = GetFallbackGlyph();
+		std::vector<float> heightBetweenLines;
+		float currentLineHeightAboveBaseline = 0;
+		float currentLineHeightBelowBaseline = 0;
+		float prevLineHeightBelowBaseline = -INFINITY;
+		float extraOffset = m_atlasData->GetAtlasType().IsBitmap() ? 0.1 : 0.05;
+		bool isMultiline = false;
+
+		for (auto begin = text.begin(), end = text.end(); begin != end;)
+		{
+			uint32_t c = utf8::next(begin, end);
+			if (c == '\n')
+			{
+				isMultiline = true;
+				if (prevLineHeightBelowBaseline != -INFINITY)
+				{
+					heightBetweenLines.push_back(std::abs(prevLineHeightBelowBaseline)
+					                             + std::abs(currentLineHeightAboveBaseline) + extraOffset);
+					prevLineHeightBelowBaseline = currentLineHeightBelowBaseline;
+				}
+				prevLineHeightBelowBaseline = currentLineHeightBelowBaseline;
+				currentLineHeightAboveBaseline = currentLineHeightBelowBaseline = 0;
+				continue;
+			}
+
+			if (!symbols.contains(c))
+			{
+				c = fallbackGlyph;
+			}
+			const GlyphInfo& info = symbols.at(c);
+			currentLineHeightAboveBaseline = std::max(currentLineHeightAboveBaseline, info.pos[2].y);
+			currentLineHeightBelowBaseline = std::min(currentLineHeightBelowBaseline, -info.pos[0].y);
+		}
+
+		if (isMultiline && text.back() != '\n')
+		{
+			heightBetweenLines.push_back(std::abs(prevLineHeightBelowBaseline)
+			                             + std::abs(currentLineHeightAboveBaseline) + extraOffset);
+		}
+		return heightBetweenLines;
+	}
+
 	void TextDrawable::GenerateText(const std::string& text, const Math::Vector2f& pos)
 	{
 		if (text.empty()) return;
@@ -93,16 +142,26 @@ namespace OpenVulkano::Scene
 		const std::map<uint32_t, GlyphInfo>& symbols = m_atlasData->GetGlyphs();
 
 		double cursorX = pos.x;
-		const double lineHeight = m_atlasData->GetLineHeight();
 		double posY = pos.y;
 		Math::Vector2f bmin(pos), bmax(pos);
 		float prevGlyphXBound = -INFINITY;
+		int currentLine = 0;
+		const std::vector<float> heightsBetweenLines = GetHeightsBetweenLines(text);
+
 		for (auto begin = text.begin(), end = text.end(); begin != end;)
 		{
 			uint32_t c = utf8::next(begin, end);
 			if (c == '\n')
 			{
-				posY -= lineHeight;
+				// use fixed line height
+				if (heightsBetweenLines.empty())
+				{
+					posY -= m_atlasData->GetLineHeight();
+				}
+				else
+				{
+					posY -= heightsBetweenLines[currentLine++];
+				}
 				prevGlyphXBound = -INFINITY;
 				cursorX = pos.x;
 				continue;
@@ -129,8 +188,14 @@ namespace OpenVulkano::Scene
 			{
 				vertices->position[i].x = info.pos[i].x + cursorX + offset;
 				vertices->uv[i] = info.uv[i];
-				if (i < 2) vertices->position[i].y = posY - info.pos[i].y;
-				else vertices->position[i].y = posY + info.pos[i].y;
+				if (i < 2)
+				{
+					vertices->position[i].y = posY - info.pos[i].y;
+				}
+				else
+				{
+					vertices->position[i].y = posY + info.pos[i].y;
+				}
 				vertices->color = m_cfg.textColor;
 				vertices->background = m_cfg.backgroundColor;
 			}
diff --git a/openVulkanoCpp/Scene/TextDrawable.hpp b/openVulkanoCpp/Scene/TextDrawable.hpp
index a57dc18..cad19dc 100644
--- a/openVulkanoCpp/Scene/TextDrawable.hpp
+++ b/openVulkanoCpp/Scene/TextDrawable.hpp
@@ -21,6 +21,7 @@ namespace OpenVulkano::Scene
 	{
 		Math::Vector4uc textColor = { 255, 255, 255, 255 };
 		Math::Vector4uc backgroundColor = { 0, 255, 0, 0 };
+		bool minimalSpacingBetweenMultipleLines = true;
 	};
 
 	struct TextGlyphVertex
@@ -41,6 +42,7 @@ namespace OpenVulkano::Scene
 		TextConfig m_cfg;
 
 		uint32_t GetFallbackGlyph() const;
+		std::vector<float> GetHeightsBetweenLines(const std::string& text) const;
 
 	public:
 		TextDrawable(const TextConfig& config = TextConfig());