From 09ece861d1f8015f4960ab5fcfc6cb599e979f3e Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Sat, 8 Jan 2022 11:36:29 -0800
Subject: [PATCH] Added the hint SDL_HINT_RENDER_LINE_METHOD to select the line
rendering method
---
include/SDL_hints.h | 13 ++++++++++++
src/render/SDL_render.c | 42 +++++++++++++++++++++++++++++++-------
src/render/SDL_sysrender.h | 11 ++++++++++
3 files changed, 59 insertions(+), 7 deletions(-)
diff --git a/include/SDL_hints.h b/include/SDL_hints.h
index 0e0908664dd..1185f42229b 100644
--- a/include/SDL_hints.h
+++ b/include/SDL_hints.h
@@ -1059,6 +1059,19 @@ extern "C" {
*/
#define SDL_HINT_RENDER_BATCHING "SDL_RENDER_BATCHING"
+/**
+ * \brief A variable controlling how the 2D render API renders lines
+ *
+ * This variable can be set to the following values:
+ * "0" - Use the default line drawing method (Bresenham's line algorithm as of SDL 2.0.20)
+ * "1" - Use the driver point API using Bresenham's line algorithm (correct, draws many points)
+ * "2" - Use the driver line API (occasionally misses line endpoints based on hardware driver quirks, was the default before 2.0.20)
+ * "3" - Use the driver geometry API (correct, draws thicker diagonal lines)
+ *
+ * This variable should be set when the renderer is created.
+ */
+#define SDL_HINT_RENDER_LINE_METHOD "SDL_RENDER_LINE_METHOD"
+
/**
* \brief A variable controlling whether to enable Direct3D 11+'s Debug Layer.
*
diff --git a/src/render/SDL_render.c b/src/render/SDL_render.c
index 2f6fe8345c5..a9251c27436 100644
--- a/src/render/SDL_render.c
+++ b/src/render/SDL_render.c
@@ -896,6 +896,26 @@ void VerifyDrawQueueFunctions(const SDL_Renderer *renderer)
SDL_assert(renderer->RunCommandQueue != NULL);
}
+static SDL_RenderLineMethod SDL_GetRenderLineMethod()
+{
+ const char *hint = SDL_GetHint(SDL_HINT_RENDER_LINE_METHOD);
+
+ int method = 0;
+ if (hint) {
+ method = SDL_atoi(hint);
+ }
+ switch (method) {
+ case 1:
+ return SDL_RENDERLINEMETHOD_POINTS;
+ case 2:
+ return SDL_RENDERLINEMETHOD_LINES;
+ case 3:
+ return SDL_RENDERLINEMETHOD_GEOMETRY;
+ default:
+ return SDL_RENDERLINEMETHOD_POINTS;
+ }
+}
+
SDL_Renderer *
SDL_CreateRenderer(SDL_Window * window, int index, Uint32 flags)
{
@@ -1011,6 +1031,8 @@ SDL_CreateRenderer(SDL_Window * window, int index, Uint32 flags)
renderer->relative_scaling = SDL_GetHintBoolean(SDL_HINT_MOUSE_RELATIVE_SCALING, SDL_TRUE);
+ renderer->line_method = SDL_GetRenderLineMethod();
+
if (SDL_GetWindowFlags(window) & (SDL_WINDOW_HIDDEN|SDL_WINDOW_MINIMIZED)) {
renderer->hidden = SDL_TRUE;
} else {
@@ -1062,6 +1084,9 @@ SDL_CreateSoftwareRenderer(SDL_Surface * surface)
/* new textures start at zero, so we start at 1 so first render doesn't flush by accident. */
renderer->render_command_generation = 1;
+ /* Software renderer always uses line method, for speed */
+ renderer->line_method = SDL_RENDERLINEMETHOD_LINES;
+
SDL_RenderSetViewport(renderer, NULL);
}
return renderer;
@@ -2794,6 +2819,10 @@ static int plotLineLow(SDL_Renderer *renderer, float x0, float y0, float x1, flo
SDL_FPoint *points = SDL_small_alloc(SDL_FPoint, count, &isstack);
SDL_FPoint *tmp = points;
+ if (!points) {
+ return SDL_OutOfMemory();
+ }
+
if (dy < 0) {
yi = -1;
dy = -dy;
@@ -2837,6 +2866,10 @@ static int plotLineHigh(SDL_Renderer *renderer, float x0, float y0, float x1, fl
SDL_FPoint *points = SDL_small_alloc(SDL_FPoint, count, &isstack);
SDL_FPoint *tmp = points;
+ if (!points) {
+ return SDL_OutOfMemory();
+ }
+
if (dx < 0) {
xi = -1;
dx = -dx;
@@ -2999,8 +3032,6 @@ SDL_RenderDrawLinesF(SDL_Renderer * renderer,
const SDL_FPoint * points, int count)
{
int retval = 0;
- int use_renderpoints;
- int use_rendergeometry;
CHECK_RENDERER_MAGIC(renderer, -1);
@@ -3018,12 +3049,9 @@ SDL_RenderDrawLinesF(SDL_Renderer * renderer,
}
#endif
- use_renderpoints = 1;
- use_rendergeometry = 1;
-
- if (use_renderpoints) {
+ if (renderer->line_method == SDL_RENDERLINEMETHOD_POINTS) {
retval = RenderDrawLinesWithRectsF(renderer, points, count);
- } else if (use_rendergeometry) {
+ } else if (renderer->line_method == SDL_RENDERLINEMETHOD_GEOMETRY) {
SDL_bool isstack1;
SDL_bool isstack2;
const float scale_x = renderer->scale.x;
diff --git a/src/render/SDL_sysrender.h b/src/render/SDL_sysrender.h
index 1500b3a355d..ff38ed0dd69 100644
--- a/src/render/SDL_sysrender.h
+++ b/src/render/SDL_sysrender.h
@@ -114,6 +114,14 @@ typedef struct SDL_VertexSolid
} SDL_VertexSolid;
+typedef enum
+{
+ SDL_RENDERLINEMETHOD_POINTS,
+ SDL_RENDERLINEMETHOD_LINES,
+ SDL_RENDERLINEMETHOD_GEOMETRY,
+} SDL_RenderLineMethod;
+
+
/* Define the SDL renderer structure */
struct SDL_Renderer
{
@@ -214,6 +222,9 @@ struct SDL_Renderer
/* Whether or not to scale relative mouse motion */
SDL_bool relative_scaling;
+ /* The method of drawing lines */
+ SDL_RenderLineMethod line_method;
+
/* Remainder from scaled relative motion */
float xrel;
float yrel;