opengl won't overlap more than 1 texture

I’m trying to create an opengl program that creates a 2d square, and applies 2 textures on it.

I followed this tutorial: https://learnopengl.com/Getting-started/Textures

This is my fragment shader:

#version 330 core

//in vec3 Color;
in vec2 TexCoord;

out vec4 FragColor;

uniform sampler2D Texture1;
uniform sampler2D Texture2;

void main()
{
    FragColor = mix(texture(Texture1, TexCoord), texture(Texture2, TexCoord), 0.5);
}

This is the code that sends the textures and the uniforms:

GLuint Tex1, Tex2;

int TexWidth, TexHeight, TexNrChannels;
unsigned char* TexData = stbi_load("container.jpg", &TexWidth, &TexHeight, &TexNrChannels, 0);
glGenTextures(1, &Tex1);
glBindTexture(GL_TEXTURE_2D, Tex1);
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);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, TexWidth, TexHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, TexData);
glGenerateMipmap(GL_TEXTURE_2D);
glUniform1i(glGetUniformLocation(Program, "Texture1"), 0);
stbi_image_free(TexData);

TexData = stbi_load("awesomeface.png", &TexWidth, &TexHeight, &TexNrChannels, 0);
glGenTextures(1, &Tex2);
glBindTexture(GL_TEXTURE_2D, Tex2);
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);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, TexWidth, TexHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, TexData);
glGenerateMipmap(GL_TEXTURE_2D);
glUniform1i(glGetUniformLocation(Program, "Texture2"), 1);
stbi_image_free(TexData);

And this is the render loop:

    while (!glfwWindowShouldClose(window))
{
    processInput(window);

    // GL render here
    glClearColor(0.05f, 0.0f, 0.1f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, Tex1);
    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, Tex2);

    glUseProgram(Program);
    glBindVertexArray(VAO);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

    glfwSwapBuffers(window);
    glfwPollEvents();
}

When I run it, only the first texture shows up on the square, and the a argument (last argument) of the mix function in the shader won’t make a difference for any value.

I tried activating (glActiveTexture + GlBindTexture) the second texture first in the render loop, and it caused the second texture to be shown exclusively.

How can I make the textures mix together like in the tutorial?

If this approach is wrong, I would like to learn about another way to accomplish the same result.

>Solution :

glUniform1i set a value in the default uniform block of the currently installed program. You have to install the program with glUseProgram, before you can set the value of a uniform variable:

GLint t1_loc = glGetUniformLocation(Program, "Texture1");
GLint t2_loc = glGetUniformLocation(Program, "Texture2");

glUseProgram(Program);
glUniform1i(t1_loc, 0);
glUniform1i(t2_loc, 1);

Alternatively you can use glProgramUniform1i:

glProgramUniform1i(Program, t1_loc, 0);
glProgramUniform1i(Program, t2_loc, 1);