关于pr#49

我的系统是MacOS 15.7 M1芯片，环境使用brew安装的，在这个pr合并后，我的example在make run会存在报错：

Assertion failed: (t != NULL), function surface2texture, file render.cpp, line 19.
make: *** [run] Abort trap: 6

于是我尝试将pr中的修改的部分注释掉后又可以正常运行。
在这之后上我将此次修改中SDL_SetHint(SDL_HINT_RENDER_DRIVER, "gpu");的gpu

• 替换为opengl能显示nvboard，但会发生闪烁的情况；
• 替换为metal后，也发生闪烁，且Display灯处带有雪花屏的效果，比opengl那个更差些。
• 更换为software是正常的。

#49

@SArthurX 想问问还会出现之前的渲染问题吗？#47

[SArthurX]

Hi @shineeve,
I still experience the issue when using other hints.

However, according to the SDL docs, this function only suggests which render driver the system should use and returns boolean, so it shouldn’t cause a compilation error.

In fact, even if I replace "gpu" with a completely non-existent string, the program still compiles successfully.

So I guess the compilation failure doesn’t seem to be directly related to SDL_SetHint.

Hi @shineeve, I still experience the issue when using other hints.

However, according to the SDL docs, this function only suggests which render driver the system should use and returns boolean, so it shouldn’t cause a compilation error.

In fact, even if I replace "gpu" with a completely non-existent string, the program still compiles successfully.

So I guess the compilation failure doesn’t seem to be directly related to SDL_SetHint.

---

感谢回复！😄 重新思考了一下。

---

• 现状：最新的代码在我的电脑上会出现返回 NULL 指针导致 assert 崩溃。回到这次pr改动前，我的nvboard通过编译并正常显示。

• 发现： SDL_HINT_RENDER_DRIVER的"gpu" 这个选项在 SDL2 docs 中不存在，但在 SDL3 docs 中发现了它。

• 猜测：代码中使用了 SDL3 特有的 API 在 SDL2 环境下运行，导致：SDL2 无法识别 "gpu" 渲染器类型->渲染器创建异常；-> 后续纹理创建 (SDL_CreateTextureFromSurface) 失败；-> 返回 NULL 指针导致 assert 崩溃。(未经验证)

---

我认为SDL_HINT_RENDER_DRIVER可能并不是必要的。SDL 应该是会自动按优先级选择最佳渲染器。如果一定要使用SDL_HINT_RENDER_DRIVER,我这边只有software是能正常的。opengl与metal都会闪烁。

跟着LLM调试了下去打印了点错误信息：

FATAL ERROR: SDL_CreateRenderer failed! 
SDL Error: Couldn't find matching render driver

然后看了下代码，发现了新东西然后就做了点小试验：注意到就在修改的下面两行根据选项分别是和显示器的刷新率同步，使用硬件加速或者软件，最后的0应该是是自动选择，在macos上也是matel > software。

main_window = SDL_CreateWindow("NVBoard " VERSION_STR, SDL_WINDOWPOS_CENTERED,
        SDL_WINDOWPOS_CENTERED, WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_SHOWN);
    main_renderer = SDL_CreateRenderer(main_window, -1, 
    #ifdef VSYNC
        SDL_RENDERER_PRESENTVSYNC |
    #endif
    #ifdef HARDWARE_ACC
        SDL_RENDERER_ACCELERATED |
    #else
        SDL_RENDERER_SOFTWARE |
    #endif
        0
    );

实验1: 保留SDL_SetHint(SDL_HINT_RENDER_DRIVER, "gpu"); 将上述代码的SDL_RENDERER_SOFTWARE | 这行删去，产生效果与SDL_SetHint(SDL_HINT_RENDER_DRIVER, "metal");一致。仍是渲染有问题。如下：

问题画面：

Screen.Recording.2025-11-16.at.22.28.16.mov

所以实际使用SDL_HINT_RENDER_DRIVER的"gpu"，等价于打开HARDWARE_ACC选项？它和软件渲染不能共存？

实验2:使用main_renderer = SDL_CreateRenderer(main_window, -1, 0)。这应该是是自动选择用什么渲染，优先级应该就是硬件>软件。

实验3：硬件加速，默认VSYNC，还是有问题的画面。

实验4: 使用软件渲染，默认VSYNC，对我来说没什么差别。是正常渲染画面。

---

暂且就这样吧，在我的环境下（M1 chip），使用metal会出现渲染问题。使用software画面正常。

diff --git a/src/nvboard.cpp b/src/nvboard.cpp
index ec240b2..4f6ff89 100644
--- a/src/nvboard.cpp
+++ b/src/nvboard.cpp
@@ -60,9 +60,6 @@ void nvboard_init(int vga_clk_cycle) {
     // init SDL and SDL_image
     SDL_Init(SDL_INIT_TIMER | SDL_INIT_VIDEO | SDL_INIT_EVENTS);
     IMG_Init(IMG_INIT_PNG);
-    #if defined(__APPLE__)
-        SDL_SetHint(SDL_HINT_RENDER_DRIVER, "gpu");
-    #endif
     
     main_window = SDL_CreateWindow("NVBoard " VERSION_STR, SDL_WINDOWPOS_CENTERED,
         SDL_WINDOWPOS_CENTERED, WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_SHOWN);

@SArthurX 我发现nix中的sdl2指向sdl2-compat。也许我们之间的差异来自于SDL版本。请问尝试真正的sdl2，还会出现#47 吗？

If you add the following code:

diff --git a/src/nvboard.cpp b/src/nvboard.cpp
index ec240b2..c3dd347 100644
--- a/src/nvboard.cpp
+++ b/src/nvboard.cpp
@@ -77,6 +77,10 @@ void nvboard_init(int vga_clk_cycle) {
     #endif
         0
     );
+    if (!main_renderer) {
+    fprintf(stderr, "❌ SDL_CreateRenderer failed: %s\n", SDL_GetError());
+    exit(1);
+    }
     SDL_SetRenderDrawColor(main_renderer, 0xff, 0xff, 0xff, 0);
     SDL_RenderFillRect(main_renderer, NULL);

you may see the output:

···
- Verilator: Walltime 3.728 s (elab=0.005, cvt=0.010, bld=3.702); cpu 0.015 s on 1 threads
❌ SDL_CreateRenderer failed: Couldn't find matching render driver
make: *** [run] Error 1
···

This shows that

• the "gpu" render driver hint cannot be used because it is not a valid option in SDL 2.
• macOS may be stricter in this regard; on Linux systems (e.g., Debian 12, where sdl2-config --version reports 2.26.5), using this hint doesn‘t cause an immediate failure.
• Nix does not provide a “pure” SDL 2 implementation. Instead, it uses sdl2-compat —a compatibility layer that internally routes SDL 2 API calls to SDL 3, which does support the "gpu" renderer, making it appear to work in that specific environment.