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

(Backed out hg changeset 7a4240daba46)

src/render/opengl/SDL_render_gl.c

@@ -848,6 +848,60 @@ GL_QueueDrawPoints(SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_FP
     return 0;
 }
 
+static int
+GL_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
 GL_QueueFillRects(SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_FRect * rects, int count)
 {
@@ -1211,59 +1265,14 @@ GL_RunCommandQueue(SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *vertic
             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);
                 SetDrawState(data, cmd, SHADER_SOLID);
-                if (count > 2 && (verts[0] == verts[(count-1)*2]) && (verts[1] == verts[(count*2)-1])) {
-                    data->glBegin(GL_LINE_LOOP);
-                    /* GL_LINE_LOOP takes care of the final segment */
-                    for (i = 1; i < count; ++i, verts += 2) {
-                        data->glVertex2f(verts[0], verts[1]);
-                    }
-                    data->glEnd();
-                } else {
-                    #if defined(__MACOSX__) || defined(__WIN32__)
-                    #else
-                    int x1, y1, x2, y2;
-                    #endif
-
-                    data->glBegin(GL_LINE_STRIP);
-                    for (i = 0; i < count; ++i, verts += 2) {
-                        data->glVertex2f(verts[0], verts[1]);
-                    }
-                    data->glEnd();
-                    verts -= 2 * count;
-
-                    /* The line is half open, so we need one more point to complete it.
-                     * http://www.opengl.org/documentation/specs/version1.1/glspec1.1/node47.html
-                     * If we have to, we can use vertical line and horizontal line textures
-                     * for vertical and horizontal lines, and then create custom textures
-                     * for diagonal lines and software render those.  It's terrible, but at
-                     * least it would be pixel perfect.
-                     */
-
-                    data->glBegin(GL_POINTS);
-                    #if defined(__MACOSX__) || defined(__WIN32__)
-                    /* Mac OS X and Windows seem to always leave the last point open */
-                    data->glVertex2f(verts[(count-1)*2], verts[(count*2)-1]);
-                    #else
-                    /* Linux seems to leave the right-most or bottom-most point open */
-                    x1 = verts[0];
-                    y1 = verts[1];
-                    x2 = verts[(count-1)*2];
-                    y2 = verts[(count*2)-1];
-
-                    if (x1 > x2) {
-                        data->glVertex2f(x1, y1);
-                    } else if (x2 > x1) {
-                        data->glVertex2f(x2, y2);
-                    }
-                    if (y1 > y2) {
-                        data->glVertex2f(x1, y1);
-                    } else if (y2 > y1) {
-                        data->glVertex2f(x2, y2);
-                    }
-                    #endif
-                    data->glEnd();
+                data->glBegin(GL_LINES);
+                for (i = 0; i < count-1; ++i, verts += 4) {
+                    data->glVertex2f(verts[0], verts[1]);
+                    data->glVertex2f(verts[2], verts[3]);
                 }
+                data->glEnd();
                 break;
             }
 
@@ -1602,7 +1611,7 @@ GL_CreateRenderer(SDL_Window * window, Uint32 flags)
     renderer->QueueSetViewport = GL_QueueSetViewport;
     renderer->QueueSetDrawColor = GL_QueueSetViewport;  /* SetViewport and SetDrawColor are (currently) no-ops. */
     renderer->QueueDrawPoints = GL_QueueDrawPoints;
-    renderer->QueueDrawLines = GL_QueueDrawPoints;  /* lines and points queue vertices the same way. */
+    renderer->QueueDrawLines = GL_QueueDrawLines;
     renderer->QueueFillRects = GL_QueueFillRects;
     renderer->QueueCopy = GL_QueueCopy;
     renderer->QueueCopyEx = GL_QueueCopyEx;

src/render/opengles/SDL_render_gles.c

@@ -561,6 +561,60 @@ GLES_QueueDrawPoints(SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_
     return 0;
 }
 
+static int
+GLES_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
 GLES_QueueFillRects(SDL_Renderer * renderer, SDL_RenderCommand *cmd, const SDL_FRect * rects, int count)
 {
@@ -901,16 +955,10 @@ GLES_RunCommandQueue(SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *vert
             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);
                 SetDrawState(data, cmd);
                 data->glVertexPointer(2, GL_FLOAT, 0, verts);
-                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;
             }
 
@@ -1159,7 +1207,7 @@ GLES_CreateRenderer(SDL_Window * window, Uint32 flags)
     renderer->QueueSetViewport = GLES_QueueSetViewport;
     renderer->QueueSetDrawColor = GLES_QueueSetViewport;  /* SetViewport and SetDrawColor are (currently) no-ops. */
     renderer->QueueDrawPoints = GLES_QueueDrawPoints;
-    renderer->QueueDrawLines = GLES_QueueDrawPoints;  /* lines and points queue vertices the same way. */
+    renderer->QueueDrawLines = GLES_QueueDrawLines;
     renderer->QueueFillRects = GLES_QueueFillRects;
     renderer->QueueCopy = GLES_QueueCopy;
     renderer->QueueCopyEx = GLES_QueueCopyEx;

src/render/opengles2/SDL_render_gles2.c

@@ -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;