c - Visual Studio:不会在子窗口中绘制矩形

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想改进这个问题吗？Update the question所以堆栈溢出的值小于aa>。
三年前关闭。
我已经创建了这3个子窗口，但现在我想在其中一个子窗口（第一个子窗口）中绘制一个矩形。我没有错误，但它没有显示任何内容（只有3个空子窗口）。。。
这是C中的代码：

#include "glut.h"
#include <stdio.h>

// ***** Main Window *****//

#define GAP  10 // gap between subwindows

//  define the window position on screen
float main_window_x;
float main_window_y;

//  variables representing the window size
float main_window_w = 256 + GAP * 2;
float main_window_h = 256 + 64 + GAP * 3;

//  variable representing the window title
char *window_title = "SubWindow Template";

//  Represents the window id
int main_window;

// ***** Sub Window 1 *****//

//  define the window position on screen
float subwindow1_x = GAP;
float subwindow1_y = GAP;

//  variables representing the window size
float subwindow1_w = 256;
float subwindow1_h = 220;

//  Represents the subwindow id
int subwindow_1;

// ***** Sub Window 2 *****//

//  define the window position on screen
float subwindow2_x = GAP;
float subwindow2_y = GAP + 220 + GAP;

//  variables representing the window size
float subwindow2_w = 123;
float subwindow2_h = 100;

//  Represents the subwindow id
int subwindow_2;

// ***** Sub Window 3 *****//

//  define the window position on screen
float subwindow3_x = GAP + 123 + GAP;
float subwindow3_y = GAP + 220 + GAP;

//  variables representing the window size
float subwindow3_w = 123;
float subwindow3_h = 100;

//  Represents the subwindow id
int subwindow_3;

void main_display(void)
{
//  Set background color to black
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

//  Swap front and back buffers
    glutSwapBuffers();
}

void subwindow1_display(void)
{
//  Set background color to white
    glClearColor(1.0, 1.0, 1.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);

//  Set drawing color to gray
    glColor3f(0.75, 0.75, 0.75);

    glBegin(GL_QUADS);
    glVertex2i(GAP + 20, GAP + 10);
    glVertex2i(GAP + 40, GAP + 10);
    glVertex2i(GAP + 40, GAP + 30);
    glVertex2i(GAP + 20, GAP + 30);

    glEnd();

    glFlush();

//  Swap front and back buffers
    glutSwapBuffers();
}

void subwindow2_display(void)
{
//  Set background color to white
    glClearColor(1.0, 1.0, 1.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);

//  Set drawing color to blue
    glColor3f(0, 0, 1);

//  Swap front and back buffers
    glutSwapBuffers();
}

void subwindow3_display(void)
{
//  Set background color to white
    glClearColor(1.0, 1.0, 1.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);

//  Set drawing color to blue
    glColor3f(0, 0, 1);

//  Swap front and back buffers
    glutSwapBuffers();
}

// ***** General *****//

//  Tells whether to display the window full screen or not
int full_screen = 0;

void main_reshape(int width, int height)
{

//  Just take the case when the user tries
//  to make the size of the window very small...
    if (width < GAP * 4 || height < GAP * 6)
    {
        glutSetWindow(main_window);
        glutReshapeWindow(main_window_w, main_window_h);
        return;
    }

//  Change the subwindow 1 dimensions as window dimensions change
//  main_window_w          ---> subwindow1_w
//  main_window_w' (width) ---> ??
//  ==>
    subwindow1_w = (subwindow1_w * (width - GAP * 2.0)) / (main_window_w - GAP * 2.0);
    subwindow1_h = (subwindow1_h * (height - GAP * 3.0)) / (main_window_h - GAP * 3.0);

//  Set subwindow 1 as current window and then reposition and resize it
    glutSetWindow(subwindow_1);
    glutPositionWindow(GAP, GAP);
    glutReshapeWindow(subwindow1_w, subwindow1_h);

//  Change the subwindow 2 dimensions as window dimensions change
    subwindow2_w = (subwindow2_w * (width - GAP * 2.0)) / (main_window_w - GAP * 2.0);
    subwindow2_h = (subwindow2_h * (height - GAP * 3.0)) / (main_window_h - GAP * 3.0);

//  Set subwindow 2 as current window and then reposition and resize it
    glutSetWindow(subwindow_2);
    glutPositionWindow(GAP, GAP + subwindow1_h + GAP);
    glutReshapeWindow(subwindow2_w, subwindow2_h);

//  Change the subwindow 3 dimensions as window dimensions change
    subwindow3_w = (subwindow3_w * (width - GAP * 2.0)) / (main_window_w - GAP * 2.0);
    subwindow3_h = (subwindow3_h * (height - GAP * 3.0)) / (main_window_h - GAP * 3.0);

//  Set subwindow 3 as current window and then reposition and resize it
    glutSetWindow(subwindow_3);
    glutPositionWindow(GAP * 2 + 123, GAP + subwindow1_h + GAP);
    glutReshapeWindow(subwindow3_w, subwindow3_h);

//  Stay updated with the window width and height
    main_window_w = width;
    main_window_h = height;

}

//-------------------------------------------------------------------------
//  SubWindow 1 Reshape Function.
//
//  Preserve aspect ratio of viewport when subwindow is resized.
//-------------------------------------------------------------------------
void subwindow1_reshape(int width, int height)
{

//  Represents a side of the viewport. A viewport is intended to
//  to take a square shape so that the aspect ratio is reserved
    int viewport_side = 0;

//  Viewport x and y positions (Center viewport)
    int viewport_x = 0, viewport_y = 0;

//  Calculate viewport side
    viewport_side = (width > height) ? height : width;

//  Calculate viewport position
    viewport_x = (width - viewport_side) / 2;
    viewport_y = (height - viewport_side) / 2;

//  Preserve aspect ratio
    glViewport(viewport_x, viewport_y, viewport_side, viewport_side);

//  Set subwindow width and height
    subwindow1_w = width;
    subwindow1_h = height;
}

//-------------------------------------------------------------------------
//  SubWindow 2 Reshape Function.
//
//  Preserve aspect ratio of viewport when subwindow is resized.
//-------------------------------------------------------------------------
void subwindow2_reshape(int width, int height)
{
//  Represents a side of the viewport. A viewport is intended to
//  to take a square shape so that the aspect ratio is reserved
    int viewport_side = 0;

//  Viewport x and y positions (Center viewport)
    int viewport_x = 0, viewport_y = 0;

//  Calculate viewport side
    viewport_side = (width > height) ? height : width;

//  Calculate viewport position
    viewport_x = (width - viewport_side) / 2;
    viewport_y = (height - viewport_side) / 2;

//  Preserve aspect ratio
    glViewport(viewport_x, viewport_y, viewport_side, viewport_side);

//  Set subwindow width and height
    subwindow2_w = width;
    subwindow2_h = height;
}

//-------------------------------------------------------------------------
//  SubWindow 3 Reshape Function.
//
//  Preserve aspect ratio of viewport when subwindow is resized.
//-------------------------------------------------------------------------
void subwindow3_reshape(int width, int height)
{
//  Represents a side of the viewport. A viewport is intended to
//  to take a square shape so that the aspect ratio is reserved
    int viewport_side = 0;

//  Viewport x and y positions (Center viewport)
    int viewport_x = 0, viewport_y = 0;

//  Calculate viewport side
    viewport_side = (width > height) ? height : width;

//  Calculate viewport position
    viewport_x = (width - viewport_side) / 2;
    viewport_y = (height - viewport_side) / 2;

//  Preserve aspect ratio
    glViewport(viewport_x, viewport_y, viewport_side, viewport_side);

//  Set subwindow width and height
    subwindow3_w = width;
    subwindow3_h = height;
}

//-------------------------------------------------------------------------
//  Redisplay contents of subwindow 1 and subwindow 2 and subwindow3.
//-------------------------------------------------------------------------
void redisplay_all(void)
{
    glutSetWindow(subwindow_1);
    glutPostRedisplay();
    glutSetWindow(subwindow_2);
    glutPostRedisplay();
    glutSetWindow(subwindow_3);
    glutPostRedisplay();
}

//-------------------------------------------------------------------------
//  This function sets the window x and y coordinates
//  such that the window becomes centered
//-------------------------------------------------------------------------
void centerOnScreen()
{
    main_window_x = (glutGet(GLUT_SCREEN_WIDTH) - main_window_w) / 2;
    main_window_y = (glutGet(GLUT_SCREEN_HEIGHT) - main_window_h) / 2;
}

//-------------------------------------------------------------------------
//  Program Main method.
//-------------------------------------------------------------------------
int main(int argc, char **argv)
{
/**** Main Window **** */
    glutInit(&argc, argv);
//  Set the main window x and y coordinates such that the
//  window becomes centered
    centerOnScreen();

    glutInitWindowSize(main_window_w, main_window_h);
    glutInitWindowPosition(main_window_x, main_window_y);
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);

    main_window = glutCreateWindow(window_title);

    glutDisplayFunc(main_display);
    glutReshapeFunc(main_reshape);

/**** Subwindow 1 **** */
    subwindow_1 = glutCreateSubWindow(main_window, subwindow1_x, subwindow1_y, subwindow1_w, subwindow1_h);

    glutDisplayFunc(subwindow1_display);
    glutReshapeFunc(subwindow1_reshape);

/**** Subwindow 2 **** */
    subwindow_2 = glutCreateSubWindow(main_window, subwindow2_x, subwindow2_y, subwindow2_w, subwindow2_h);

    glutDisplayFunc(subwindow2_display);
    glutReshapeFunc(subwindow2_reshape);

/**** Subwindow 3 **** */
    subwindow_3 = glutCreateSubWindow(main_window, subwindow3_x, subwindow3_y, subwindow3_w, subwindow3_h);

    glutDisplayFunc(subwindow3_display);
    glutReshapeFunc(subwindow3_reshape);

//  View in full screen if the full_screen flag is on
    if (full_screen)
        glutFullScreen();

//  Start GLUT event processing loop
    glutMainLoop();

    return 0;
}

最佳答案

那个四边形离身份投影截锥不远。
设置“投影”和/或“模型视图”矩阵，以便您的四边形实际上可见：

void subwindow1_display(void)
{
    //  Set background color to white
    glClearColor(0.0, 1.0, 1.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);

    //  Set drawing color to gray
    glColor3f(0.75, 0.75, 0.75);

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    glOrtho( -50, 50, -50, 50, -1 , 1 );

    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();

    glBegin(GL_QUADS);
    glVertex2i(GAP + 20, GAP + 10);
    glVertex2i(GAP + 40, GAP + 10);
    glVertex2i(GAP + 40, GAP + 30);
    glVertex2i(GAP + 20, GAP + 30);

    glEnd();

    glFlush();

    //  Swap front and back buffers
    glutSwapBuffers();
}

关于c - Visual Studio:不会在子窗口中绘制矩形，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/36159953/