From c2bacc63b00809350b06dfaa77be51de10cfabd1 Mon Sep 17 00:00:00 2001
From: Nicolas Silva <nical@fastmail.com>
Date: Thu, 11 Aug 2022 16:50:57 +0200
Subject: [PATCH] Fix the calculation and validation of layer and mip ranges in
 create_texture_view.

The previous code was doing "selector.layers = base_layer .. count" instead of "base_layer .. base_layer + count" which looked dubious. Same thing for the mip range. It was also not taking the base layer count when in requested_layer_count when the texture was not a texture array which led to invalid ranges and underflow when asking for a non-zero base layer with a (non-array) 2d texture.
---
 wgpu-core/src/device/mod.rs | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/wgpu-core/src/device/mod.rs b/wgpu-core/src/device/mod.rs
index b3d8247ee41..51b08e6629e 100644
--- a/wgpu-core/src/device/mod.rs
+++ b/wgpu-core/src/device/mod.rs
@@ -948,18 +948,21 @@ impl<A: HalApi> Device<A> {
             },
         };
 
-        let required_level_count =
-            desc.range.base_mip_level + desc.range.mip_level_count.map_or(1, |count| count.get());
+        let mip_count = desc.range.mip_level_count.map_or(1, |count| count.get());
+        let required_level_count = desc.range.base_mip_level.saturating_add(mip_count);
+
         let required_layer_count = match desc.range.array_layer_count {
-            Some(count) => desc.range.base_array_layer + count.get(),
+            Some(count) => desc.range.base_array_layer.saturating_add(count.get()),
             None => match view_dim {
                 wgt::TextureViewDimension::D1
                 | wgt::TextureViewDimension::D2
                 | wgt::TextureViewDimension::D3 => 1,
                 wgt::TextureViewDimension::Cube => 6,
                 _ => texture.desc.array_layer_count(),
-            },
+            }
+            .max(desc.range.base_array_layer.saturating_add(1)),
         };
+
         let level_end = texture.full_range.mips.end;
         let layer_end = texture.full_range.layers.end;
         if required_level_count > level_end {
@@ -1002,17 +1005,9 @@ impl<A: HalApi> Device<A> {
             });
         }
 
-        let end_level = desc
-            .range
-            .mip_level_count
-            .map_or(level_end, |_| required_level_count);
-        let end_layer = desc
-            .range
-            .array_layer_count
-            .map_or(layer_end, |_| required_layer_count);
         let selector = TextureSelector {
-            mips: desc.range.base_mip_level..end_level,
-            layers: desc.range.base_array_layer..end_layer,
+            mips: desc.range.base_mip_level..required_level_count,
+            layers: desc.range.base_array_layer..required_layer_count,
         };
 
         let view_layer_count = selector.layers.end - selector.layers.start;