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Improve text rendering quality #3353

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Aug 6, 2023
Merged

Improve text rendering quality #3353

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93 changes: 86 additions & 7 deletions src/core/StelPainter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -51,13 +51,15 @@ QMutex* StelPainter::globalMutex = new QMutex();

QCache<QByteArray, StringTexture> StelPainter::texCache(TEX_CACHE_LIMIT);
QOpenGLShaderProgram* StelPainter::texturesShaderProgram=Q_NULLPTR;
QOpenGLShaderProgram* StelPainter::textShaderProgram=Q_NULLPTR;
QOpenGLShaderProgram* StelPainter::basicShaderProgram=Q_NULLPTR;
QOpenGLShaderProgram* StelPainter::colorShaderProgram=Q_NULLPTR;
QOpenGLShaderProgram* StelPainter::texturesColorShaderProgram=Q_NULLPTR;
QOpenGLShaderProgram* StelPainter::wideLineShaderProgram=Q_NULLPTR;
QOpenGLShaderProgram* StelPainter::colorfulWideLineShaderProgram=Q_NULLPTR;
StelPainter::BasicShaderVars StelPainter::basicShaderVars;
StelPainter::TexturesShaderVars StelPainter::texturesShaderVars;
StelPainter::TextShaderVars StelPainter::textShaderVars;
StelPainter::BasicShaderVars StelPainter::colorShaderVars;
StelPainter::TexturesColorShaderVars StelPainter::texturesColorShaderVars;
StelPainter::WideLineShaderVars StelPainter::wideLineShaderVars;
Expand Down Expand Up @@ -665,9 +667,6 @@ struct StringTexture

StringTexture* StelPainter::getTextTexture(const QString& str, int pixelSize) const
{
// Render first the text into a QPixmap, then create a QOpenGLTexture
// from it. We could optimize by directly using a QImage, but for some
// reason the result is not exactly the same than with a QPixmap.
QByteArray hash = str.toUtf8() + QByteArray::number(pixelSize);
StringTexture* cachedTex = texCache.object(hash);
if (cachedTex)
Expand All @@ -679,14 +678,15 @@ StringTexture* StelPainter::getTextTexture(const QString& str, int pixelSize) co
int w = strRect.width()+1+static_cast<int>(0.02f*strRect.width());
int h = strRect.height();

QPixmap strImage = QPixmap(StelUtils::getBiggerPowerOfTwo(w), StelUtils::getBiggerPowerOfTwo(h));
strImage.fill(Qt::transparent);
QImage strImage(StelUtils::getBiggerPowerOfTwo(w), StelUtils::getBiggerPowerOfTwo(h),
QImage::Format_RGBX8888);
strImage.fill(Qt::black);
QPainter painter(&strImage);
painter.setRenderHints(QPainter::TextAntialiasing);
painter.setFont(tmpFont);
painter.setPen(Qt::white);
painter.drawText(-strRect.x(), -strRect.y(), str);
StringTexture* newTex = new StringTexture(new QOpenGLTexture(strImage.toImage()), QSize(w, h), QPoint(strRect.x(), -(strRect.y()+h)));
StringTexture* newTex = new StringTexture(new QOpenGLTexture(strImage), QSize(w, h), QPoint(strRect.x(), -(strRect.y()+h)));
newTex->texture->setMinMagFilters(QOpenGLTexture::Linear, QOpenGLTexture::Linear);
texCache.insert(hash, newTex, 3*w*h);
// simply returning newTex is dangerous as the object is owned by the cache now. (Coverity Scan barks.)
Expand Down Expand Up @@ -745,7 +745,44 @@ void StelPainter::drawText(float x, float y, const QString& str, float angleDeg,
setBlending(true);
enableClientStates(true, true);
setVertexPointer(2, GL_FLOAT, vertexData);
drawFromArray(TriangleStrip, 4, 0, false);

const Mat4f& m = getProjector()->getProjectionMatrix();
const QMatrix4x4 qMat(m[0], m[4], m[8], m[12],
m[1], m[5], m[9], m[13],
m[2], m[6], m[10], m[14],
m[3], m[7], m[11], m[15]);

vao->bind();
verticesVBO->bind();
const GLsizeiptr vertexCount = 4;

auto& pr = *textShaderProgram;
pr.bind();

const auto bufferSize = vertexArray.vertexSizeInBytes()*vertexCount +
texCoordArray.vertexSizeInBytes()*vertexCount;
verticesVBO->allocate(bufferSize);
const auto vertexDataSize = vertexArray.vertexSizeInBytes()*vertexCount;
verticesVBO->write(0, vertexArray.pointer, vertexDataSize);
const auto texCoordDataOffset = vertexDataSize;
const auto texCoordDataSize = texCoordArray.vertexSizeInBytes()*vertexCount;
verticesVBO->write(texCoordDataOffset, texCoordArray.pointer, texCoordDataSize);

pr.setAttributeBuffer(textShaderVars.vertex, vertexArray.type, 0, vertexArray.size);
pr.enableAttributeArray(textShaderVars.vertex);
pr.setUniformValue(textShaderVars.projectionMatrix, qMat);
pr.setUniformValue(textShaderVars.textColor, currentColor.toQVector());
pr.setAttributeBuffer(textShaderVars.texCoord, texCoordArray.type,
texCoordDataOffset, texCoordArray.size);
pr.enableAttributeArray(textShaderVars.texCoord);

glDrawArrays(TriangleStrip, 0, vertexCount);

verticesVBO->release();
vao->release();

pr.release();

setBlending(oldBlending, oldSrc, oldDst);
enableClientStates(false, false);
tex->texture->release();
Expand Down Expand Up @@ -2057,6 +2094,48 @@ void StelPainter::initGLShaders()
colorShaderVars.color = colorShaderProgram->attributeLocation("color");
colorShaderVars.vertex = colorShaderProgram->attributeLocation("vertex");

// Text shader program
QOpenGLShader textVShader(QOpenGLShader::Vertex);
const auto textVSrc =
StelOpenGL::globalShaderPrefix(StelOpenGL::VERTEX_SHADER) + R"(
ATTRIBUTE highp vec3 vertex;
ATTRIBUTE mediump vec2 texCoord;
uniform mediump mat4 projectionMatrix;
VARYING mediump vec2 texc;
void main()
{
gl_Position = projectionMatrix * vec4(vertex, 1.);
texc = texCoord;
})";
textVShader.compileSourceCode(textVSrc);
if (!textVShader.log().isEmpty())
qWarning().noquote() << "StelPainter: Warnings while compiling text vertex shader: " << textVShader.log();

QOpenGLShader textFShader(QOpenGLShader::Fragment);
const auto textFSrc =
StelOpenGL::globalShaderPrefix(StelOpenGL::FRAGMENT_SHADER) + R"(
VARYING mediump vec2 texc;
uniform sampler2D tex;
uniform mediump vec4 textColor;
void main()
{
float mask = texture2D(tex, texc).r;
FRAG_COLOR = vec4(textColor.rgb, textColor.a*mask);
})";
textFShader.compileSourceCode(textFSrc);
if (!textFShader.log().isEmpty())
qWarning().noquote() << "StelPainter: Warnings while compiling text fragment shader: " << textFShader.log();

textShaderProgram = new QOpenGLShaderProgram(QOpenGLContext::currentContext());
textShaderProgram->addShader(&textVShader);
textShaderProgram->addShader(&textFShader);
linkProg(textShaderProgram, "textShaderProgram");
textShaderVars.projectionMatrix = textShaderProgram->uniformLocation("projectionMatrix");
textShaderVars.texCoord = textShaderProgram->attributeLocation("texCoord");
textShaderVars.vertex = textShaderProgram->attributeLocation("vertex");
textShaderVars.textColor = textShaderProgram->uniformLocation("textColor");
textShaderVars.texture = textShaderProgram->uniformLocation("tex");

// Basic texture shader program
QOpenGLShader vshader2(QOpenGLShader::Vertex);
const auto vsrc2 =
Expand Down
10 changes: 10 additions & 0 deletions src/core/StelPainter.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -422,6 +422,16 @@ class StelPainter : protected QOpenGLFunctions
static QOpenGLShaderProgram* colorShaderProgram;
static BasicShaderVars colorShaderVars;

static QOpenGLShaderProgram* textShaderProgram;
struct TextShaderVars {
int projectionMatrix;
int texCoord;
int vertex;
int textColor;
int texture;
};
static TextShaderVars textShaderVars;

static QOpenGLShaderProgram* texturesShaderProgram;
struct TexturesShaderVars {
int projectionMatrix;
Expand Down