Updated test case for Cinder's gl::TextureFont

gistfile1.cpp

/*
 * TESTING UNICODE FONT RENDERING WITH gl::TextureFont
 *
 * FOLLOW-UP QUESTION IN THE CINDER FORUM:
 * https://forum.libcinder.org/#Topic/23286000001505051
 *
 * COMMENTS:
 * 1) IDEALLY, WE WOULD LIKE TO BE ABLE TO PRECALCULATE THE SIZE
 *    OF A TextBox AND TO COMPUTE ITS LAYOUT IN THE SAME PASS
 * 2) THE CURRENT SYSTEM FOR DISPLAYING ARBITRARY SCALED TEXT
 *    IS NOT PRACTICAL
 * 3) USING RGBA TEXTURES IS NOT OPTIMAL IN TERM OF GPU MEMORY
 *    AND IT FORCES US TO DEAL WITH PREMULTIPLICATION
 */

#include "cinder/app/AppNative.h"
#include "cinder/gl/TextureFont.h"

using namespace ci;
using namespace ci::app;
using namespace std;

const string text = "This is a long sentence that should split over a few good lines, hopefully!";
const ColorA color = ColorA(1, 1, 0, 1);
const float alpha = 0.85f;

const float scale = 0.75f;
const Vec2f anchor = Vec2f(30, 50);

class Application : public AppNative
{
public:
    Font font;
    gl::TextureFontRef textureFont;
    
    TextBox textBox;
    Rectf bounds;
    vector<pair<uint16_t,Vec2f>> glyphMeasures;
    
    gl::TextureFont::DrawOptions options;
    
    void setup();
    void draw();
};

void Application::setup()
{
    /*
     * XXX: PREMULTIPLICATION IS REQUIRED IN ORDER TO AVOID "DIRTY TEXT" WHEN SCALE IS NOT 1.0
     * XXX: MIPMAPPING IS REQUIRED FOR PROPER AND EFFICIENT SCALING
     * XXX: NO NEED TO MONOPOLIZE A HUGE 1024x1024 TEXTURE
     */
    gl::TextureFont::Format format;
    format.textureWidth(512).textureHeight(512).premultiply(true).enableMipmapping();
    
    font = Font("Helvetica", 32);
    textureFont = gl::TextureFont::create(font, format, gl::TextureFont::defaultChars());
    
    /*
     * ISSUE 1: THIS IS CREATING A DEFAULT Font WHICH ENDS-UP BEHING UNUSED
     */
    textBox = TextBox().font(font).text(text).size(320, TextBox::GROW);
    
    /*
     * ISSUE 2, PART A: THIS IS INVOKING TextBox::createLines()
     */
    Vec2f size = textBox.measure() * scale;
    bounds = Rectf(0, 0, size.x, size.y);
   
    /*
     * ISSUE 2, PART B: THIS IS (AGAIN) INVOKING TextBox::createLines()
     */
    glyphMeasures = textBox.measureGlyphs();
    
    /*
     * XXX: PIXEL-SNAP MUST BE DISABLED FOR SCALING TO WORK PROPERLY
     */
    options = gl::TextureFont::DrawOptions().pixelSnap(false).scale(scale);
    
    // ---
    
    /*
     * XXX: REQUIRED IN ORDER TO AVOID "DIRTY TEXT" WHEN SCALE IS NOT 1.0
     */
    gl::enableAlphaBlending(true);
    
    glDepthMask(GL_FALSE);
    glDisable(GL_DEPTH_TEST);
}

void Application::draw()
{
    gl::clear(Color(0.5f, 0.5f, 0.5f), false);
    gl::setMatricesWindow(getWindowSize());

    // ---
    
    gl::color(Color(1.0f, 0.5f, 0.0f));
    gl::drawSolidRect(bounds + anchor);

    /*
     * XXX: COLOR MUST BE MULTIPLIED BY ALPHA
     */
    gl::color(color * alpha);
    textureFont->drawGlyphs(glyphMeasures, Vec2f(0, textureFont->getAscent()) * scale + anchor, options);
}

CINDER_APP_NATIVE(Application, RendererGl(0))