[android] allow to run on Android 6.0

NOTES:
regs.window_origin.flip_y MUST flip the y coordinate of any given FragCoord, we don't emulate this, this is the root cause of the error, but I'll just revert for now since it's easier

DON'T MERGE unless it's near 0.0.4 and I (or someone else) hasn't tackled this yet properly

This reverts commit 17fe74ef11.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3075
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Co-authored-by: lizzie <lizzie@eden-emu.dev>
Co-committed-by: lizzie <lizzie@eden-emu.dev>

src/android/app/build.gradle.kts

@@ -58,7 +58,7 @@ android {
 
     defaultConfig {
         applicationId = "dev.eden.eden_emulator"
-        minSdk = 24
+        minSdk = 23
         targetSdk = 36
         versionName = getGitVersion()
         versionCode = autoVersion

src/video_core/renderer_vulkan/vk_rasterizer.cpp

@@ -62,29 +62,41 @@ struct DrawParams {
 VkViewport GetViewportState(const Device& device, const Maxwell& regs, size_t index, float scale) {
     const auto& src = regs.viewport_transform[index];
     const auto conv = [scale](float value) {
-        float const new_value = value * scale;
-        return scale < 1.0f
-            ? std::round(std::abs(new_value)) * (std::signbit(new_value) ? -1.f : 1.f)
-            : new_value;
+        float new_value = value * scale;
+        if (scale < 1.0f) {
+            const bool sign = std::signbit(value);
+            new_value = std::round(std::abs(new_value));
+            new_value = sign ? -new_value : new_value;
+        }
+        return new_value;
     };
-    float const w = src.scale_x;
-    float h = src.scale_y;
-    if (regs.window_origin.mode == Maxwell::WindowOrigin::Mode::LowerLeft) // Flip by surface clip height
-        h = -h;
-    if (!device.IsNvViewportSwizzleSupported() && src.swizzle.y == Maxwell::ViewportSwizzle::NegativeY) // Flip by viewport height
-        h = -h;
-    // In theory, a raster flip is equivalent to a texture flip for a whole square viewport
-    // TODO: one day implement this properly and raster flip the triangles, not the whole viewport... guh
-    if(regs.viewport_transform[1].scale_y == 0 && regs.window_origin.flip_y != 0)
-        h = -h;
-    float const x = src.translate_x - w;
-    float const y = src.translate_y - h;
-    float const reduce_z = regs.depth_mode == Maxwell::DepthMode::MinusOneToOne ? 1.0f : 0.0f;
+    const float x = conv(src.translate_x - src.scale_x);
+    const float width = conv(src.scale_x * 2.0f);
+    float y = conv(src.translate_y - src.scale_y);
+    float height = conv(src.scale_y * 2.0f);
+
+    const bool lower_left = regs.window_origin.mode != Maxwell::WindowOrigin::Mode::UpperLeft;
+    const bool y_negate = !device.IsNvViewportSwizzleSupported() &&
+                          src.swizzle.y == Maxwell::ViewportSwizzle::NegativeY;
+
+    if (lower_left) {
+        // Flip by surface clip height
+        y += conv(static_cast<f32>(regs.surface_clip.height));
+        height = -height;
+    }
+
+    if (y_negate) {
+        // Flip by viewport height
+        y += height;
+        height = -height;
+    }
+
+    const float reduce_z = regs.depth_mode == Maxwell::DepthMode::MinusOneToOne ? 1.0f : 0.0f;
     VkViewport viewport{
-        .x = conv(x),
-        .y = conv(y),
-        .width = w != 0.0f ? conv(w * 2.f) : 1.0f,
-        .height = h != 0.0f ? conv(h * 2.f) : 1.0f,
+        .x = x,
+        .y = y,
+        .width = width != 0.0f ? width : 1.0f,
+        .height = height != 0.0f ? height : 1.0f,
         .minDepth = src.translate_z - src.scale_z * reduce_z,
         .maxDepth = src.translate_z + src.scale_z,
     };
@@ -1014,10 +1026,10 @@ void RasterizerVulkan::UpdateViewportsState(Tegra::Engines::Maxwell3D::Regs& reg
         return;
     }
     if (!regs.viewport_scale_offset_enabled) {
-        float x = float(regs.surface_clip.x);
-        float y = float(regs.surface_clip.y);
-        float width = (std::max)(1.0f, float(regs.surface_clip.width));
-        float height = (std::max)(1.0f, float(regs.surface_clip.height));
+        float x = static_cast<float>(regs.surface_clip.x);
+        float y = static_cast<float>(regs.surface_clip.y);
+        float width = (std::max)(1.0f, static_cast<float>(regs.surface_clip.width));
+        float height = (std::max)(1.0f, static_cast<float>(regs.surface_clip.height));
         if (regs.window_origin.mode != Maxwell::WindowOrigin::Mode::UpperLeft) {
             y += height;
             height = -height;