OpenGL texturing doesn't - c++

Question

A few day ago i applied the latest Window 8.1 update to my Laptop, when restarting as part of the process i got a bluescreen and so did i when i tried to manually restart etc. In the end i had to do the partial reset (it removes anything windows recognizes as an app but leaves your data intact) you are offered because i could not lose the data.
Before that incident my code for displaying textured and animated models worked but after that i got new errors from my GLSL compilers because of deprecated keywords. When those were fixed my program won't show me textures and instead just display everything black.
I have 2 older projects using the same glsl code and they also have the same problem (although they did not have any deprecated keywords in the shader).
The code worked like this ~2 hours before i did the update.
Initialising:
void TestWindow::initialize()
{
initSkybox();
initVAO();
initVBO();
m_program = new QOpenGLShaderProgram(this);
m_program->addShaderFromSourceFile(QOpenGLShader::Vertex ,"../Qt_Flyff_1/Simple_VertexShader.vert");
m_program->addShaderFromSourceFile(QOpenGLShader::Fragment ,"../Qt_Flyff_1/Simple_FragmentShader.frag");
m_program->link();
qDebug("log: %s",m_program->log().toStdString().c_str());
m_posAttr = m_program->attributeLocation("position");
m_texPos = m_program->attributeLocation("texcoord");
m_colorUniform = m_program->uniformLocation("color");
m_matrixUniform = m_program->uniformLocation("matrix");
int asdf=m_program->uniformLocation("tex");
GLuint tex;
glGenTextures(1, &tex);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, tex);
QImage img("../skybox01_big.png");
glTexImage2D(GL_TEXTURE_2D, 0, GL_BGRA, img.width(), img.height(), 0, GL_BGRA, GL_UNSIGNED_BYTE, img.bits());
glGenerateMipmap(GL_TEXTURE_2D);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_NEAREST);
glEnable(GL_DEPTH_TEST);
// glEnable(GL_CULL_FACE);
glClearColor(0.5,0.5,0.5,1.0);
m_program->setUniformValue(asdf,0);
}
Vertex Shader:
#version 400 core
uniform mediump mat4 matrix;
uniform mediump vec3 color;
in vec4 position;
in vec2 texcoord;
out vec3 Color;
out vec2 Texcoord;
void main()
{
Color = color;
Texcoord = texcoord;
gl_Position = matrix*position;
}
Fragment Shader:
#version 400 core
in vec3 Color;
in vec2 Texcoord;
out vec4 outColor;
uniform sampler2D tex;
void main()
{
outColor = texture(tex, Texcoord) * vec4(Color, 1.0);
}
I've also compared my code to various tutorials and could not find any difference.
When simply using "outColor = vec4(Color,1.0)" my model is completly white as expected and when displaying the texture coordinates as color i also get the expected results.
In case it matters my Laptop has a GeForce GT 740M.

Answer 1

Ok i found the solution.
What i didn't know is that there is a difference between internalformat and format for glTexImage2D.
The format specifies what the data you send to the GPU looks like and the internalformat is what the GPU uses internally and this allows less formats. My texture was stored as BGRA in the memory but OpenGL does not allow that format.
Basicly i had to change:
glTexImage2D(GL_TEXTURE_2D, 0, GL_BGRA, img.width(), img.height(), 0, GL_BGRA, GL_UNSIGNED_BYTE, img.bits());
to
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, img.width(), img.height(), 0, GL_BGRA, GL_UNSIGNED_BYTE, img.bits());
(3rd parameter from GL_BGRA to GL_RGBA)
Info on what types can be used for internalformat can be found here:
https://www.opengl.org/sdk/docs/man/html/glTexImage2D.xhtml