From ae1b97a6dd961ca31a032995abbcca24aad5e01f Mon Sep 17 00:00:00 2001
From: Zephyron <zephyron@citron-emu.org>
Date: Mon, 8 Dec 2025 16:20:12 +1000
Subject: [PATCH] fix(vulkan): Fix viewport handling when transformations are
 disabled

When viewport_scale_offset_enabled is false, properly set all viewports
using surface_clip dimensions instead of just one. This prevents vertex
explosions caused by invalid or zero-sized viewports.

- Set all viewports (Maxwell::NumViewports) when transformations disabled
- Ensure minimum viewport dimensions (1.0f) to prevent zero-sized viewports
- Respect device viewport limits when setting viewports
- Use proper viewport array instead of single viewport

Signed-off-by: Zephyron <zephyron@citron-emu.org>
---
 .../renderer_vulkan/vk_rasterizer.cpp         | 29 +++++++++++++------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/video_core/renderer_vulkan/vk_rasterizer.cpp b/src/video_core/renderer_vulkan/vk_rasterizer.cpp
index 82890e4a8..ed8a89a40 100644
--- a/src/video_core/renderer_vulkan/vk_rasterizer.cpp
+++ b/src/video_core/renderer_vulkan/vk_rasterizer.cpp
@@ -1045,15 +1045,26 @@ void RasterizerVulkan::UpdateViewportsState(Tegra::Engines::Maxwell3D::Regs& reg
         const auto y = static_cast<float>(regs.surface_clip.y);
         const auto width = static_cast<float>(regs.surface_clip.width);
         const auto height = static_cast<float>(regs.surface_clip.height);
-        VkViewport viewport{
-            .x = x,
-            .y = y,
-            .width = width != 0.0f ? width : 1.0f,
-            .height = height != 0.0f ? height : 1.0f,
-            .minDepth = 0.0f,
-            .maxDepth = 1.0f,
-        };
-        scheduler.Record([viewport](vk::CommandBuffer cmdbuf) { cmdbuf.SetViewport(0, viewport); });
+        // Ensure valid viewport dimensions to prevent vertex explosions
+        const float viewport_width = width > 0.0f ? width : 1.0f;
+        const float viewport_height = height > 0.0f ? height : 1.0f;
+
+        std::array<VkViewport, Maxwell::NumViewports> viewport_list;
+        for (size_t i = 0; i < Maxwell::NumViewports; ++i) {
+            viewport_list[i] = VkViewport{
+                .x = x,
+                .y = y,
+                .width = viewport_width,
+                .height = viewport_height,
+                .minDepth = 0.0f,
+                .maxDepth = 1.0f,
+            };
+        }
+        scheduler.Record([this, viewport_list](vk::CommandBuffer cmdbuf) {
+            const u32 num_viewports = std::min<u32>(device.GetMaxViewports(), Maxwell::NumViewports);
+            const vk::Span<VkViewport> viewports(viewport_list.data(), num_viewports);
+            cmdbuf.SetViewport(0, viewports);
+        });
         return;
     }
     const bool is_rescaling{texture_cache.IsRescaling()};