Create a text shader and font utility

scwx-qt/source/scwx/qt/gl/text_shader.cpp

@@ -0,0 +1,155 @@
+#include <scwx/qt/gl/text_shader.hpp>
+
+#include <boost/log/trivial.hpp>
+#include <glm/gtc/type_ptr.hpp>
+
+namespace scwx
+{
+namespace qt
+{
+namespace gl
+{
+
+static const std::string logPrefix_ = "[scwx::qt::gl::text_shader] ";
+
+class TextShaderImpl
+{
+public:
+   explicit TextShaderImpl(OpenGLFunctions& gl) :
+       gl_ {gl},
+       projectionLocation_(GL_INVALID_INDEX),
+       textColorLocation_(GL_INVALID_INDEX),
+       vao_ {GL_INVALID_INDEX},
+       vbo_ {GL_INVALID_INDEX}
+   {
+   }
+
+   ~TextShaderImpl() {}
+
+   OpenGLFunctions& gl_;
+
+   GLint projectionLocation_;
+   GLint textColorLocation_;
+
+   GLuint vao_;
+   GLuint vbo_;
+};
+
+TextShader::TextShader(OpenGLFunctions& gl) :
+    ShaderProgram(gl), p(std::make_unique<TextShaderImpl>(gl))
+{
+}
+TextShader::~TextShader() = default;
+
+TextShader::TextShader(TextShader&&) noexcept = default;
+TextShader& TextShader::operator=(TextShader&&) noexcept = default;
+
+bool TextShader::Initialize()
+{
+   OpenGLFunctions& gl = p->gl_;
+
+   // Load and configure shader
+   bool success = Load(":/gl/text.vert", ":/gl/text.frag");
+
+   p->projectionLocation_ = gl.glGetUniformLocation(id(), "projection");
+   if (p->projectionLocation_ == -1)
+   {
+      BOOST_LOG_TRIVIAL(warning) << logPrefix_ << "Could not find projection";
+   }
+
+   p->textColorLocation_ = gl.glGetUniformLocation(id(), "textColor");
+   if (p->textColorLocation_ == -1)
+   {
+      BOOST_LOG_TRIVIAL(warning) << logPrefix_ << "Could not find textColor";
+   }
+
+   gl.glGenVertexArrays(1, &p->vao_);
+   gl.glGenBuffers(1, &p->vbo_);
+   gl.glBindVertexArray(p->vao_);
+   gl.glBindBuffer(GL_ARRAY_BUFFER, p->vbo_);
+   gl.glBufferData(
+      GL_ARRAY_BUFFER, sizeof(float) * 6 * 4, nullptr, GL_DYNAMIC_DRAW);
+   gl.glEnableVertexAttribArray(0);
+   gl.glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(float), 0);
+   gl.glBindBuffer(GL_ARRAY_BUFFER, 0);
+   gl.glBindVertexArray(0);
+
+   return success;
+}
+
+void TextShader::RenderText(const std::string&               text,
+                            float                            x,
+                            float                            y,
+                            float                            scale,
+                            const glm::mat4&                 projection,
+                            const boost::gil::rgba8_pixel_t& color,
+                            const std::unordered_map<char, util::Glyph>& glyphs)
+{
+   OpenGLFunctions& gl = p->gl_;
+
+   Use();
+
+   gl.glEnable(GL_BLEND);
+   gl.glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+   gl.glUniformMatrix4fv(
+      p->projectionLocation_, 1, GL_FALSE, glm::value_ptr(projection));
+   gl.glUniform4f(
+      p->textColorLocation_, color[0], color[1], color[2], color[3]);
+
+   gl.glActiveTexture(GL_TEXTURE0);
+   gl.glBindVertexArray(p->vao_);
+
+   for (auto c = text.cbegin(); c != text.cend(); c++)
+   {
+      if (glyphs.find(*c) == glyphs.end())
+      {
+         continue;
+      }
+
+      const util::Glyph& g = glyphs.at(*c);
+
+      float xpos = x + g.bearing.x * scale;
+      float ypos = y - (g.size.y - g.bearing.y) * scale;
+
+      float w = g.size.x * scale;
+      float h = g.size.y * scale;
+
+      // Glyph vertices
+      float vertices[6][4] = {{xpos, ypos + h, 0.0f, 0.0f},
+                              {xpos, ypos, 0.0f, 1.0f},
+                              {xpos + w, ypos, 1.0f, 1.0f}, //
+                                                            //
+                              {xpos, ypos + h, 0.0f, 0.0f},
+                              {xpos + w, ypos, 1.0f, 1.0f},
+                              {xpos + w, ypos + h, 1.0f, 0.0f}};
+
+      // Render glyph texture
+      gl.glBindTexture(GL_TEXTURE_2D, g.textureId);
+
+      gl.glBindBuffer(GL_ARRAY_BUFFER, p->vbo_);
+      gl.glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
+      gl.glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+      gl.glDrawArrays(GL_TRIANGLES, 0, 6);
+
+      // Advance to the next glyph
+      x += (g.advance >> 6) * scale;
+   }
+}
+
+void TextShader::SetProjection(const glm::mat4& projection)
+{
+   p->gl_.glUniformMatrix4fv(
+      p->projectionLocation_, 1, GL_FALSE, glm::value_ptr(projection));
+}
+
+void TextShader::SetTextColor(const boost::gil::rgba8_pixel_t color)
+{
+   p->gl_.glUniform4f(
+      p->textColorLocation_, color[0], color[1], color[2], color[3]);
+}
+
+} // namespace gl
+} // namespace qt
+} // namespace scwx