基於OpenGL的RoundBox繪制

實現了16種roundBox，見圖

核心繪制碼在RoundBox.h文件：

#ifndef ROUNDBOXRENDER_H
#define ROUNDBOXRENDER_H
struct RoundBoxRender
{
 // 產生一個漸變的效果：
 //  shadetop疊加top
 //  shadedown疊加到down 可以為負
 //  rad為圓角的半徑
 /* linear horizontal shade within button or in outline */
 /* view2d scrollers use it */
 static void gl_round_box_shade(int mode, float minx, float miny, float maxx, float maxy, float rad, float shadetop, float shadedown)
 {
  float vec[7][2]= {{0.195, 0.02}, {0.383, 0.067}, {0.55, 0.169}, {0.707, 0.293},
  {0.831, 0.45}, {0.924, 0.617}, {0.98, 0.805}};
  float div= maxy-miny;
  float coltop[3], coldown[3], color[4];
  int a;
  /* mult */
  for(a=0; a<7; a++) {
   vec[a][0]*= rad; vec[a][1]*= rad;
  }
  /* get current color, needs to be outside of glBegin/End */
  glGetFloatv(GL_CURRENT_COLOR, color);
  /* 'shade' defines strength of shading */ 
  coltop[0]= color[0]+shadetop; if(coltop[0]>1.0) coltop[0]= 1.0;
  coltop[1]= color[1]+shadetop; if(coltop[1]>1.0) coltop[1]= 1.0;
  coltop[2]= color[2]+shadetop; if(coltop[2]>1.0) coltop[2]= 1.0;
  coldown[0]= color[0]+shadedown; if(coldown[0]<0.0) coldown[0]= 0.0;
  coldown[1]= color[1]+shadedown; if(coldown[1]<0.0) coldown[1]= 0.0;
  coldown[2]= color[2]+shadedown; if(coldown[2]<0.0) coldown[2]= 0.0;
  glShadeModel(GL_SMOOTH);
  glBegin(mode);
  /* start with corner right-bottom */
  if(roundboxtype & 4) {
   round_box_shade_col(coltop, coldown, 0.0);
   glVertex2f(maxx-rad, miny);
   for(a=0; a<7; a++) {
    round_box_shade_col(coltop, coldown, vec[a][1]/div);
    glVertex2f(maxx-rad+vec[a][0], miny+vec[a][1]);
   }
   round_box_shade_col(coltop, coldown, rad/div);
   glVertex2f(maxx, miny+rad);
  }
  else {
   round_box_shade_col(coltop, coldown, 0.0);
   glVertex2f(maxx, miny);
  }
  /* corner right-top */
  if(roundboxtype & 2) {
   round_box_shade_col(coltop, coldown, (div-rad)/div);
   glVertex2f(maxx, maxy-rad);
   for(a=0; a<7; a++) {
    round_box_shade_col(coltop, coldown, (div-rad+vec[a][1])/div);
    glVertex2f(maxx-vec[a][1], maxy-rad+vec[a][0]);
   }
   round_box_shade_col(coltop, coldown, 1.0);
   glVertex2f(maxx-rad, maxy);
  }
  else {
   round_box_shade_col(coltop, coldown, 1.0);
   glVertex2f(maxx, maxy);
  }
  /* corner left-top */
  if(roundboxtype & 1) {
   round_box_shade_col(coltop, coldown, 1.0);
   glVertex2f(minx+rad, maxy);
   for(a=0; a<7; a++) {
    round_box_shade_col(coltop, coldown, (div-vec[a][1])/div);
    glVertex2f(minx+rad-vec[a][0], maxy-vec[a][1]);
   }
   round_box_shade_col(coltop, coldown, (div-rad)/div);
   glVertex2f(minx, maxy-rad);
  }
  else {
   round_box_shade_col(coltop, coldown, 1.0);
   glVertex2f(minx, maxy);
  }
  /* corner left-bottom */
  if(roundboxtype & 8) {
   round_box_shade_col(coltop, coldown, rad/div);
   glVertex2f(minx, miny+rad);
   for(a=0; a<7; a++) {
    round_box_shade_col(coltop, coldown, (rad-vec[a][1])/div);
    glVertex2f(minx+vec[a][1], miny+rad-vec[a][0]);
   }
   round_box_shade_col(coltop, coldown, 0.0);
   glVertex2f(minx+rad, miny);
  }
  else {
   round_box_shade_col(coltop, coldown, 0.0);
   glVertex2f(minx, miny);
  }
  glEnd();
  glShadeModel(GL_FLAT);
 }
 static void setType(int nType){
  roundboxtype = nType % 16;
 }
protected:
 static void round_box_shade_col(float *col1, float *col2, float fac)
 {
  float col[3];
  col[0]= (fac*col1[0] + (1.0-fac)*col2[0]);
  col[1]= (fac*col1[1] + (1.0-fac)*col2[1]);
  col[2]= (fac*col1[2] + (1.0-fac)*col2[2]);
  glColor3fv(col);
 }
 static int roundboxtype;
};
int RoundBoxRender::roundboxtype = 3;
#endif