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POcan't draw item after I get it from queue
 

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  1. POcan't draw item after I get it from queue
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    <p>I've got three <code>CustomPixel</code> objects - when I draw it directly in draw function <code>draw</code> - it works normal.</p> <p>But when I put them into <code>queue</code> and draw them one after another with <code>while</code> loop - there are not any rectangles on the screen.</p> <p>Here is my code</p> <pre><code>#include &lt;gl\glew.h&gt; #include &lt;gl\freeglut.h&gt; #include &lt;iostream&gt; #include "OpenGL.h" #include "Constants.h" #include "Geometrics.h" #include &lt;queue&gt; std::queue&lt;CustomPixel*&gt; queue; CustomPixel *pixel1 = new CustomPixel(0.0, 250.0, 100.0); CustomPixel *pixel2 = new CustomPixel(101.0, 250.0, 100.0); CustomPixel *pixel3 = new CustomPixel(202.0, 250.0, 100.0); void draw() { glClear(GL_COLOR_BUFFER_BIT); glBegin(GL_POINTS); pixel1-&gt;drawRectangle(1.0, 0.0, 0.0); //it works! if (!queue.empty()) { while(!queue.empty()) { CustomPixel *item = queue.front(); //doesn't work -&gt; but //in debugger it enters this method with correct CustomPixel //attributes(x1, x2...etc) item-&gt;drawRectangle(1.0, 0.0, 0.0); queue.pop(); } } glEnd(); glFlush(); }; int main(int iArgc, char** cppArgv) { //console for debug OpenGL *opengl = new OpenGL(iArgc, cppArgv); opengl-&gt;setSize(WIDTH, HEIGHT); opengl-&gt;setWindowPosition(200, 200); opengl-&gt;create(); //after OpenGL object created -&gt; fill the queue with objects and the draw it queue.push(pixel1); queue.push(pixel2); queue.push(pixel3); opengl-&gt;run(draw);//&lt;- can be any draw function //clean all garbage delete pixel1; delete pixel2; delete pixel3; delete opengl; return 0; } </code></pre> <p>P.S it has been a long time since I used c++. Maybe I forgot something?</p> <p>Here drawRectangle method</p> <pre><code>void CustomPixel::drawRectangle(float r, float g, float b) { glColor3f(r, g, b); CustomLine::drawLine(this-&gt;x1, this-&gt;y1, this-&gt;x1, this-&gt;y2); CustomLine::drawLine(this-&gt;x1, this-&gt;y1, this-&gt;x2, this-&gt;y1); CustomLine::drawLine(this-&gt;x2, this-&gt;y1, this-&gt;x2, this-&gt;y2); CustomLine::drawLine(this-&gt;x2, this-&gt;y2, this-&gt;x1, this-&gt;y2); }; </code></pre> <p>and drawLine</p> <pre><code>void CustomLine::drawLine(float x1, float y1, float x2, float y2) { float dx = (x2 - x1) / STEP; float dy = (y2 - y1) / STEP; float vX = x1 / WIDTH; float vY = y1 / HEIGHT; for(int i = 0; i &lt; STEP; i++) { glVertex2f(vX + dx * i / WIDTH, vY + dy * i / HEIGHT); } }; </code></pre>
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    1. PTQuestion
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    1. USlapots
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    1. COThere is nothing wrong with your use of std::queue here. (As you have noticed in your comment). Is it possible that the gl*() calls (or are they macros?) have to be called in the same scope as drawRectangle()?
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      1. POcan't draw item after I get it from queue
      1. USnamezero
    2. COWhere is `drawRectangle (...)`'s implementation? There are a lot of OpenGL operations that are invalid between `glBegin` and `glEnd`, if you trigger even just 1 invalid operation at the end of `drawRectangle (...)` then all subsequent calls to `drawRectangle (...)` in your begin/end block will have undefined results.
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      1. POcan't draw item after I get it from queue
      1. USAndon M. Coleman
    3. COIt looks like it works the first time. Then everything is popped off the list and `draw()` is called repeatedly. So the first render is `glClear`ed and nothing more gets rendered.
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      1. POcan't draw item after I get it from queue
      1. USjozxyqk
 

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