Text alignment and point size

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

@@ -55,11 +55,12 @@ bool TextShader::Initialize()
 void TextShader::RenderText(const std::string&               text,
                             float                            x,
                             float                            y,
-                            float                            scale,
+                            float                            pointSize,
                             const glm::mat4&                 projection,
                             const boost::gil::rgba8_pixel_t& color,
                             std::shared_ptr<util::Font>      font,
-                            GLuint                           textureId)
+                            GLuint                           textureId,
+                            TextAlign                        align)
 {
    OpenGLFunctions& gl = p->gl_;
 
@@ -74,9 +75,26 @@ void TextShader::RenderText(const std::string&               text,
    gl.glActiveTexture(GL_TEXTURE0);
    gl.glBindTexture(GL_TEXTURE_2D, textureId);
 
+   switch (align)
+   {
+   case TextAlign::Left:
+      // Do nothing
+      break;
+
+   case TextAlign::Center:
+      // X position is the center of text, subtract half length
+      x -= font->TextLength(text, pointSize) * 0.5f;
+      break;
+
+   case TextAlign::Right:
+      // X position is the end of text, subtract length
+      x -= font->TextLength(text, pointSize);
+      break;
+   }
+
    std::shared_ptr<util::FontBuffer> buffer =
       std::make_shared<util::FontBuffer>();
-   font->BufferText(buffer, text, x, y, scale, color);
+   font->BufferText(buffer, text, x, y, pointSize, color);
    buffer->Render(gl);
 }
 

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

@@ -15,6 +15,13 @@ namespace qt
 namespace gl
 {
 
+enum class TextAlign
+{
+   Left,
+   Center,
+   Right
+};
+
 class TextShaderImpl;
 
 class TextShader : public ShaderProgram
@@ -37,7 +44,8 @@ public:
                    const glm::mat4&                 projection,
                    const boost::gil::rgba8_pixel_t& color,
                    std::shared_ptr<util::Font>      font,
-                   GLuint                           textureId);
+                   GLuint                           textureId,
+                   TextAlign                        align = TextAlign::Left);
    void SetProjection(const glm::mat4& projection);
 
 private:

scwx-qt/source/scwx/qt/util/font.cpp

@@ -62,6 +62,9 @@ static const std::string CODEPOINTS =
 
 static const std::string logPrefix_ = "[scwx::qt::util::font] ";
 
+static constexpr float BASE_POINT_SIZE = 72.0f;
+static constexpr float POINT_SCALE     = 1.0f / BASE_POINT_SIZE;
+
 static std::unordered_map<std::string, std::shared_ptr<Font>> fontMap_;
 
 class FontImpl
@@ -96,11 +99,13 @@ float Font::BufferText(std::shared_ptr<FontBuffer> buffer,
                        const std::string&          text,
                        float                       x,
                        float                       y,
-                       float                       scale,
+                       float                       pointSize,
                        boost::gil::rgba8_pixel_t   color) const
 {
    static constexpr float colorScale = 1.0f / 255.0f;
 
+   const float scale = pointSize * POINT_SCALE;
+
    float r = color[0] * colorScale;
    float g = color[1] * colorScale;
    float b = color[2] * colorScale;
@@ -154,8 +159,10 @@ float Font::Kerning(char c1, char c2) const
    return 0.0f;
 }
 
-float Font::TextLength(const std::string& text, float scale) const
+float Font::TextLength(const std::string& text, float pointSize) const
 {
+   const float scale = pointSize * POINT_SCALE;
+
    float x = 0.0f;
 
    for (size_t i = 0; i < text.length(); ++i)
@@ -232,7 +239,7 @@ std::shared_ptr<Font> Font::Create(const std::string& resource)
 
    font->p->atlas_                   = ftgl::texture_atlas_new(512, 512, 1);
    ftgl::texture_font_t* textureFont = ftgl::texture_font_new_from_memory(
-      font->p->atlas_, 72, fontData.constData(), fontData.size());
+      font->p->atlas_, BASE_POINT_SIZE, fontData.constData(), fontData.size());
 
    textureFont->rendermode = ftgl::RENDER_SIGNED_DISTANCE_FIELD;
 

scwx-qt/source/scwx/qt/util/font.hpp

@@ -33,10 +33,10 @@ public:
                     const std::string&          text,
                     float                       x,
                     float                       y,
-                    float                       scale,
+                    float                       pointSize,
                     boost::gil::rgba8_pixel_t   color) const;
    float Kerning(char c1, char c2) const;
-   float TextLength(const std::string& text, float scale) const;
+   float TextLength(const std::string& text, float pointSize) const;
 
    GLuint GenerateTexture(OpenGLFunctions& gl);