From aa8200beedd993b5cd5c8c9cefe338e601451f45 Mon Sep 17 00:00:00 2001
From: Gary Talent <gary@drinkingtea.net>
Date: Sat, 27 Jan 2024 23:39:03 -0600
Subject: [PATCH] [glutils] Add helper functions for setting up shaders

---
 deps/glutils/include/glutils/glutils.hpp | 34 ++++++++++++++++-
 deps/glutils/src/glutils.cpp             | 48 +++++++++++++++++++++---
 2 files changed, 76 insertions(+), 6 deletions(-)

diff --git a/deps/glutils/include/glutils/glutils.hpp b/deps/glutils/include/glutils/glutils.hpp
index 037c6b4e..da55cfa4 100644
--- a/deps/glutils/include/glutils/glutils.hpp
+++ b/deps/glutils/include/glutils/glutils.hpp
@@ -150,8 +150,38 @@ class FrameBufferBind {
 
 void bind(const FrameBuffer &fb) noexcept;
 
+struct ShaderVarSet {
+	GLsizei len{};
+	ox::String name;
+};
 
-ox::Result<GLProgram> buildShaderProgram(ox::CStringView const&vert, ox::CStringView const&frag, ox::CStringView const&geo = "") noexcept;
+struct ProgramSource {
+	ox::Vector<glutils::ShaderVarSet> const shaderParams;
+	GLsizei const rowLen = [this] {
+		GLsizei len{};
+		for (auto const&v : shaderParams) {
+			len += v.len;
+		}
+		return len;
+	}();
+	ox::String const vertShader{};
+	ox::String const fragShader{};
+	ox::String const geomShader{};
+};
+
+ox::Result<GLProgram> buildShaderProgram(ProgramSource const&src) noexcept;
+
+ox::Result<GLProgram> buildShaderProgram(
+		ox::CStringView const&vert,
+		ox::CStringView const&frag,
+		ox::CStringView const&geo = "") noexcept;
+
+void setupShaderParams(
+		GLProgram const&shader,
+		ox::Vector<ShaderVarSet> const&vars,
+		GLsizei vertexRowLen) noexcept;
+
+void setupShaderParams(GLProgram const&shader, ox::Vector<ShaderVarSet> const&vars) noexcept;
 
 glutils::GLVertexArray generateVertexArrayObject() noexcept;
 
@@ -160,6 +190,8 @@ glutils::GLBuffer generateBuffer() noexcept;
 [[nodiscard]]
 FrameBuffer generateFrameBuffer(int width, int height) noexcept;
 
+void resizeFrameBuffer(FrameBuffer &fb, int width, int height) noexcept;
+
 /**
  * Resizes a FrameBuffer, and creates if it does not already exist.
  */
diff --git a/deps/glutils/src/glutils.cpp b/deps/glutils/src/glutils.cpp
index bd1ca0c8..f1eaf0cf 100644
--- a/deps/glutils/src/glutils.cpp
+++ b/deps/glutils/src/glutils.cpp
@@ -88,6 +88,40 @@ static ox::Result<GLShader> buildShader(
 	return shader;
 }
 
+ox::Result<GLProgram> buildShaderProgram(ProgramSource const&src) noexcept {
+	oxRequireM(program, buildShaderProgram(
+			src.vertShader,
+			src.fragShader,
+			src.geomShader));
+	setupShaderParams(program, src.shaderParams, src.rowLen);
+	return std::move(program);
+}
+
+void setupShaderParams(
+		GLProgram const&shader,
+		ox::Vector<ShaderVarSet> const&vars,
+		GLsizei vertexRowLen) noexcept {
+	// setup vars
+	for (auto lenWritten = 0LU; auto const&v : vars) {
+		auto const attr = static_cast<GLuint>(glGetAttribLocation(shader, v.name.c_str()));
+		glEnableVertexAttribArray(attr);
+		glVertexAttribPointer(
+				attr, v.len, GL_FLOAT, GL_FALSE,
+				vertexRowLen * static_cast<GLsizei>(sizeof(float)),
+				std::bit_cast<void*>(uintptr_t{lenWritten * sizeof(float)}));
+		lenWritten += static_cast<size_t>(v.len);
+	}
+}
+
+void setupShaderParams(GLProgram const&shader, ox::Vector<ShaderVarSet> const&vars) noexcept {
+	// get row len
+	GLsizei vertexRowLen{};
+	for (auto const&v : vars) {
+		vertexRowLen += v.len;
+	}
+	setupShaderParams(shader, vars, vertexRowLen);
+}
+
 ox::Result<GLProgram> buildShaderProgram(
 		ox::CStringView const&vert,
 		ox::CStringView const&frag,
@@ -147,11 +181,7 @@ FrameBuffer generateFrameBuffer(int width, int height) noexcept {
 	return fb;
 }
 
-void resizeInitFrameBuffer(FrameBuffer &fb, int width, int height) noexcept {
-	if (!fb) {
-		fb = generateFrameBuffer(width, height);
-		return;
-	}
+void resizeFrameBuffer(FrameBuffer &fb, int width, int height) noexcept {
 	width = ox::max(1, width);
 	height = ox::max(1, height);
 	fb.width = width;
@@ -171,6 +201,14 @@ void resizeInitFrameBuffer(FrameBuffer &fb, int width, int height) noexcept {
 	glBindRenderbuffer(GL_RENDERBUFFER, 0);
 }
 
+void resizeInitFrameBuffer(FrameBuffer &fb, int width, int height) noexcept {
+	if (!fb) {
+		fb = generateFrameBuffer(width, height);
+		return;
+	}
+	resizeFrameBuffer(fb, width, height);
+}
+
 void resizeInitFrameBuffer(FrameBuffer &fb, ox::Size const&sz) noexcept {
 	resizeInitFrameBuffer(fb, sz.width, sz.height);
 }