在调整大小之前，无法识别OpenGL视口设置(OpenGL Viewport setting not recognized until resize)

 我正在阅读“C＃Game Programming for Serious Game Creation”一书中的例子，我看到了一些奇怪的行为。 我设置了一个视口和正交投影，然后尝试绘制一个50px宽的三角形。 我一开始只看到三角形的一小部分，但是当我调整窗口大小（例如，最大化然后恢复）时，三角形突然显示为正确的大小。 
 
 这是一个重现问题的简单示例： 
 
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Tao.OpenGl;

namespace SimpleExample
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            _openGLControl.InitializeContexts();
        }

        protected override void OnClientSizeChanged(EventArgs e)
        {
            base.OnClientSizeChanged(e);

            int width = ClientSize.Width;
            int height = ClientSize.Height;
            double halfWidth = (double)width / 2;
            double halfHeight = (double)height / 2;

            Gl.glViewport(0, 0, width, height);
            Gl.glMatrixMode(Gl.GL_PROJECTION);
            Gl.glLoadIdentity();
            Gl.glOrtho(-halfWidth, halfWidth, -halfHeight, halfHeight, -100, 100);
            Gl.glMatrixMode(Gl.GL_MODELVIEW);
            Gl.glLoadIdentity();
        }

        private void _openGLControl_Paint(object sender, PaintEventArgs e)
        {
            Gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
            Gl.glClear(Gl.GL_COLOR_BUFFER_BIT);

            Gl.glBegin(Gl.GL_TRIANGLE_STRIP);
            {
                Gl.glColor4d(1.0, 0.0, 0.0, 0.5);
                Gl.glVertex3d(-50, 0, 0);
                Gl.glColor3d(0.0, 1.0, 0.0);
                Gl.glVertex3d(50, 0, 0);
                Gl.glColor3d(0.0, 0.0, 1.0);
                Gl.glVertex3d(0, 50, 0);

            }
            Gl.glEnd();
            Gl.glFinish();
        }
    }
}
 
 在绘制三角形之前程序启动时会触发OnClientSizeChanged事件，但在调整窗口大小之前，视口/正交似乎没有任何改变。 
 
 我正在使用OpenTk库并包含Tao.OpenGL（如您所见）。 我在我的表单上使用SimpleOpenGlControl，其中Dock设置为Fill。 在Windows 7上运行VS2012。我希望尽可能贴近书中的示例，而不是使用过剩或任何额外的库。 谁能指出我做错了什么？ 

I am going through the examples in the book "C# Game Programming For Serious Game Creation" and am seeing some strange behavior. I set a viewport and the ortho projection and then try to draw a triangle 50px wide. I am only seeing a tiny portion of the triangle at first, but when I resize the window (e.g., maximize and then restore), the triangle suddenly shows as the correct size.
 
Here is a simple example that reproduces the issue:
 
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Tao.OpenGl;

namespace SimpleExample
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            _openGLControl.InitializeContexts();
        }

        protected override void OnClientSizeChanged(EventArgs e)
        {
            base.OnClientSizeChanged(e);

            int width = ClientSize.Width;
            int height = ClientSize.Height;
            double halfWidth = (double)width / 2;
            double halfHeight = (double)height / 2;

            Gl.glViewport(0, 0, width, height);
            Gl.glMatrixMode(Gl.GL_PROJECTION);
            Gl.glLoadIdentity();
            Gl.glOrtho(-halfWidth, halfWidth, -halfHeight, halfHeight, -100, 100);
            Gl.glMatrixMode(Gl.GL_MODELVIEW);
            Gl.glLoadIdentity();
        }

        private void _openGLControl_Paint(object sender, PaintEventArgs e)
        {
            Gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
            Gl.glClear(Gl.GL_COLOR_BUFFER_BIT);

            Gl.glBegin(Gl.GL_TRIANGLE_STRIP);
            {
                Gl.glColor4d(1.0, 0.0, 0.0, 0.5);
                Gl.glVertex3d(-50, 0, 0);
                Gl.glColor3d(0.0, 1.0, 0.0);
                Gl.glVertex3d(50, 0, 0);
                Gl.glColor3d(0.0, 0.0, 1.0);
                Gl.glVertex3d(0, 50, 0);

            }
            Gl.glEnd();
            Gl.glFinish();
        }
    }
}
 
The OnClientSizeChanged event does get triggered when the program starts before the triangle is drawn, but the viewport/ortho don't seem to change anything until I resize the window.
 
I am using the OpenTk library and including Tao.OpenGL (as you can see). I am using a SimpleOpenGlControl on my form which has Dock set to Fill. Running in VS2012 on Windows 7. I would like to stick as close as possible to the book examples, and not use glut or any extra libraries. Can anyone point out what I'm doing wrong?

原文：https://stackoverflow.com/questions/16903234