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render: Restoring line rendering fixes that were previously put on hold.

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(Backed out hg changeset 7a4240daba46)
This commit is contained in:
Ryan C. Gordon 2020-10-20 11:12:49 -04:00
parent 0360987f45
commit c33f808354
3 changed files with 175 additions and 71 deletions
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67
src/render/opengles2/SDL_render_gles2.c
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@ -783,6 +783,60 @@ GLES2_QueueDrawPoints(SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL
return 0;
}
static int
GLES2_QueueDrawLines(SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_FPoint * points, int count)
{
GLfloat *verts;
int i;
SDL_assert(count >= 2); /* should have been checked at the higher level. */
verts = (GLfloat *) SDL_AllocateRenderVertices(renderer, (count-1) * 4 * sizeof (GLfloat), 0, &cmd->data.draw.first);
if (!verts) {
return -1;
}
cmd->data.draw.count = count;
/* GL_LINE_STRIP seems to be unreliable on various drivers, so try
to build out our own GL_LINES. :(
If the line segment is completely horizontal or vertical,
make it one pixel longer, to satisfy the diamond-exit rule.
We should probably do this for diagonal lines too, but we'd have to
do some trigonometry to figure out the correct pixel and generally
when we have problems with pixel perfection, it's for straight lines
that are missing a pixel that frames something and not arbitrary
angles. Maybe !!! FIXME for later, though. */
for (i = 0; i < count-1; i++, points++) {
GLfloat xstart = 0.5f + points[0].x; /* 0.5f to get to the center of the pixel. */
GLfloat ystart = 0.5f + points[0].y;
GLfloat xend = 0.5f + points[1].x;
GLfloat yend = 0.5f + points[1].y;
if (xstart == xend) { /* vertical line */
if (yend > ystart) {
yend += 1.0f;
} else {
ystart += 1.0f;
}
} else if (ystart == yend) { /* horizontal line */
if (xend > xstart) {
xend += 1.0f;
} else {
xstart += 1.0f;
}
}
*(verts++) = xstart;
*(verts++) = ystart;
*(verts++) = xend;
*(verts++) = yend;
}
return 0;
}
static int
GLES2_QueueFillRects(SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_FRect * rects, int count)
{
@ -1294,17 +1348,10 @@ GLES2_RunCommandQueue(SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *ver
}
case SDL_RENDERCMD_DRAW_LINES: {
const GLfloat *verts = (GLfloat *) (((Uint8 *) vertices) + cmd->data.draw.first);
const size_t count = cmd->data.draw.count;
SDL_assert(count >= 2);
if (SetDrawState(data, cmd, GLES2_IMAGESOURCE_SOLID) == 0) {
if (count > 2 && (verts[0] == verts[(count-1)*2]) && (verts[1] == verts[(count*2)-1])) {
/* GL_LINE_LOOP takes care of the final segment */
data->glDrawArrays(GL_LINE_LOOP, 0, (GLsizei) (count - 1));
} else {
data->glDrawArrays(GL_LINE_STRIP, 0, (GLsizei) count);
/* We need to close the endpoint of the line */
data->glDrawArrays(GL_POINTS, (GLsizei) (count - 1), 1);
}
data->glDrawArrays(GL_LINES, 0, (GLsizei) ((count-1) * 2));
}
break;
}
@ -2099,7 +2146,7 @@ GLES2_CreateRenderer(SDL_Window *window, Uint32 flags)
renderer->QueueSetViewport = GLES2_QueueSetViewport;
renderer->QueueSetDrawColor = GLES2_QueueSetViewport; /* SetViewport and SetDrawColor are (currently) no-ops. */
renderer->QueueDrawPoints = GLES2_QueueDrawPoints;
renderer->QueueDrawLines = GLES2_QueueDrawPoints; /* lines and points queue vertices the same way. */
renderer->QueueDrawLines = GLES2_QueueDrawLines;
renderer->QueueFillRects = GLES2_QueueFillRects;
renderer->QueueCopy = GLES2_QueueCopy;
renderer->QueueCopyEx = GLES2_QueueCopyEx;