feat(ww3d2): add IRenderBackend Interface by bobtista · Pull Request #2613 · TheSuperHackers/GeneralsGameCode

bobtista · 2026-04-17T23:33:37Z

Summary

First PR in a planned multi-step refactor introducing an IRenderBackend interface in WW3D2. This PR adds only the scaffolding — interface, adapter, lifecycle wiring, and one isolated proof-of-concept call site. zero behavior change. The DX8 path remains the only renderer; g_renderBackend is constructed as a DX8Backend that forwards every method to the existing DX8Wrapper static facade.

What this PR adds

IRenderBackend.h — abstract interface covering the W3D-facing subset of DX8Wrapper's public API. Only high-level methods (those taking ShaderClass/TextureBaseClass/Matrix4x4/etc.) are virtualized. D3D8-typed low-level methods stay on DX8Wrapper as DX8Backend-specific escape hatches — see the doc for the rationale.
DX8Backend.{h,cpp} — concrete adapter that forwards every virtual method to the existing DX8Wrapper:: static functions. Pure forwarding, no new rendering logic.
RenderBackend.{h,cpp} — exposes the global IRenderBackend* g_renderBackend. Init_Render_Backend() constructs new DX8Backend() from DX8Wrapper::Do_Onetime_Device_Dependent_Inits(); Shutdown_Render_Backend() tears it down from DX8Wrapper::Do_Onetime_Device_Dependent_Shutdowns().

Test plan

Windows CI builds pass
Game launches and runs a Skirmish round identically (no visual / behavioral difference)

greptile-apps · 2026-04-17T23:48:13Z

Greptile Summary

Introduces IRenderBackend, a virtual interface abstracting the W3D-facing subset of DX8Wrapper, along with DX8Backend (a pure forwarding adapter) and the g_renderBackend global lifecycle managed through Init_Render_Backend/Shutdown_Render_Backend. The DX8 rendering path is unchanged; this is scaffolding only.

IRenderBackend.h — new abstract interface with ~40 pure-virtual methods covering scene, draw, transform, texture, and light operations; also defines the D3D-independent RenderBackendViewport struct and TransformKind enum.
DX8Backend.{h,cpp} — concrete one-liner trampolines to every DX8Wrapper static; Initialize/Shutdown are no-ops as DX8Wrapper owns the device.
RenderBackend.{h,cpp} + dx8wrapper.cpp — lifecycle hooks wired into Do_Onetime_Device_Dependent_Inits/Shutdowns; the shutdown call site dereferences g_renderBackend before the null guard in Shutdown_Render_Backend.

Confidence Score: 4/5

Safe to merge after fixing the unguarded g_renderBackend dereference in the shutdown path.

The shutdown path in dx8wrapper.cpp calls g_renderBackend->Shutdown() directly before the null guard inside Shutdown_Render_Backend(), so any code path reaching Do_Onetime_Device_Dependent_Shutdowns() without a prior successful init will crash. The rest of the change is mechanical forwarding with no new logic.

Core/Libraries/Source/WWVegas/WW3D2/dx8wrapper.cpp — the shutdown block needs a null guard before dereferencing g_renderBackend.

Important Files Changed

Filename	Overview
Core/Libraries/Source/WWVegas/WW3D2/dx8wrapper.cpp	Wires Init/Shutdown into the DX8 device lifecycle; shutdown path calls g_renderBackend->Shutdown() without a null guard before the guarded Shutdown_Render_Backend(), creating a crash if reached before Init runs.
Core/Libraries/Source/WWVegas/WW3D2/IRenderBackend.h	New abstract interface covering the W3D-facing DX8Wrapper API; TransformKind enum pins values to D3DTS_* constants, leaking a D3D8 ABI detail into the backend-agnostic interface.
Core/Libraries/Source/WWVegas/WW3D2/Backend/DX8Backend.h	Concrete adapter header; all overrides declared with virtual but without the override specifier, missing compile-time mismatch detection.
Core/Libraries/Source/WWVegas/WW3D2/Backend/DX8Backend.cpp	Pure one-line trampolines to DX8Wrapper static methods; Set_Viewport and Set_Transform include correct struct/enum conversions. No issues found.
Core/Libraries/Source/WWVegas/WW3D2/Backend/RenderBackend.cpp	Owns the g_renderBackend global; Init/Shutdown functions have correct null guards internally.
Core/Libraries/Source/WWVegas/WW3D2/Backend/RenderBackend.h	Declares the g_renderBackend extern and the two lifecycle functions; clean header with #pragma once.
Core/Libraries/Source/WWVegas/WW3D2/CMakeLists.txt	Adds the four new Backend/ sources and IRenderBackend.h to the WW3D2 source list; straightforward and correct.

Class Diagram

%%{init: {'theme': 'neutral'}}%%
classDiagram
    class IRenderBackend {
        <<abstract>>
        +Initialize(window, width, height)
        +Shutdown()
        +Is_Device_Lost() bool
        +Begin_Scene()
        +End_Scene(flip_frame)
        +Set_Shader(shader)
        +Set_Texture(stage, texture)
        +Set_Transform(kind, matrix)
        +Draw_Triangles(...)
    }
    class DX8Backend {
        +Is_Device_Lost() bool
        +Begin_Scene()
        +End_Scene(flip_frame)
        +Set_Shader(shader)
        +Set_Texture(stage, texture)
        +Set_Transform(kind, matrix)
        +Draw_Triangles(...)
    }
    class DX8Wrapper {
        <<static facade>>
        +Is_Device_Lost()$
        +Begin_Scene()$
        +Set_Transform(type, matrix)$
        +Draw_Triangles(...)$
        +Do_Onetime_Device_Dependent_Inits()$
        +Do_Onetime_Device_Dependent_Shutdowns()$
    }
    class RenderBackend {
        <<global>>
        +g_renderBackend IRenderBackend*
        +Init_Render_Backend()
        +Shutdown_Render_Backend()
    }
    IRenderBackend <|-- DX8Backend : implements
    DX8Backend --> DX8Wrapper : forwards every call to
    DX8Wrapper --> RenderBackend : calls Init/Shutdown
    RenderBackend o-- IRenderBackend : owns g_renderBackend

Prompt To Fix All With AI

Fix the following 3 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 3
Core/Libraries/Source/WWVegas/WW3D2/dx8wrapper.cpp:460-461
`g_renderBackend->Shutdown()` is called unconditionally before `Shutdown_Render_Backend()`, which contains the null guard. If `Do_Onetime_Device_Dependent_Shutdowns()` is ever reached without a paired `Do_Onetime_Device_Dependent_Inits()` — for example through an error-recovery path that resets the device partway through initialization — this is a null-pointer dereference crash. The guard should wrap both calls.

```suggestion
	if (g_renderBackend != nullptr)
	{
		g_renderBackend->Shutdown();
	}
	Shutdown_Render_Backend();
```

### Issue 2 of 3
Core/Libraries/Source/WWVegas/WW3D2/IRenderBackend.h:46-51
`TransformKind` values are pinned to the D3DTS_* integer constants — including the non-sequential `RB_TRANSFORM_WORLD = 256` — so `DX8Backend` can cast them directly. This leaks a D3D8 ABI detail into the abstract interface: any future non-D3D backend will receive magic numbers (2, 3, 256) it must silently understand to mean View/Projection/World. Consider sequential values (0, 1, 2) in the interface and letting `DX8Backend::Set_Transform` map them to the D3D8 constants locally.

### Issue 3 of 3
Core/Libraries/Source/WWVegas/WW3D2/Backend/DX8Backend.h:35-103
All overriding virtual methods use only `virtual` without `override`. The `override` specifier would catch any signature mismatch between `DX8Backend` and `IRenderBackend` at compile time. Prefer `virtual ... override` (or just `override` without `virtual`) for all overriding declarations.

_{Reviews (4): Last reviewed commit: "feat(ww3d2): add IRenderBackend Initiali..." | Re-trigger Greptile}

xezon

Logical approach in an effort to start introducing new render backends. Some open questions.

xezon · 2026-05-30T10:51:03Z

+// Create the render backend. Called by DX8Wrapper::Do_Onetime_Device_Dependent_Inits
+// after the D3D device has been successfully created.
+//
+// Phase 1 always creates a DX8Backend. Phase 2 will add a compile-time


I suggest only describe the status quo, not Phase 2 futures.

xezon · 2026-05-30T10:52:54Z

+// during device teardown. Never null between those two calls.
+extern IRenderBackend * g_renderBackend;
+
+// Create the render backend. Called by DX8Wrapper::Do_Onetime_Device_Dependent_Inits


I am not fond of the function declarations explaining which third parties calls it, because the callers can change and then these comments are outdated. Several times.

xezon · 2026-05-30T10:54:44Z

+// that migrating callers is a mechanical `DX8Wrapper::X(...)` →
+// `g_renderBackend->X(...)` rewrite with minimal diff noise.
+//
+// **This header is included from VC6-compiled translation units** (the


This section goes into way too many details. This applies to the whole code base.

xezon · 2026-05-30T10:57:22Z

+        return;
+    }
+
+    // Phase 1: the DX8 backend is the only option. Phase 2 will introduce


Please make a pass on comments and clean them up.

xezon · 2026-05-30T10:59:02Z

+	// TheSuperHackers @refactor bobtista 10/04/2026 Construct the global
+	// IRenderBackend instance now that the D3D device is ready. See
+	// Core/Libraries/Source/WWVegas/WW3D2/RENDER_BACKEND.md.
+	Init_Render_Backend();


This looks suspicious. Shouldn't Init_Render_Backend call DX8Wrapper::Do_Onetime_Device_Dependent_Inits instead?

I don't think so. The contract is: DX8Wrapper owns when the renderer comes up (it owns the D3D device), and the backend owns how it brings up its own device. To make that explicit rather than implied, I'll add a lifecycle pair to the interface eg Initialize(hwnd, w, h) / Shutdown() with empty default bodies, called after Init_Render_Backend() and before Shutdown_Render_Backend(). DX8Backend treats them as no-ops since DX8Wrapper still owns the real device, and non-DX8 backends use Initialize() to create their own device/swapchain against the game window. Device-lost/reset stays DX8-internal, it's a D3D8 artifact, and modern backends recover via swapchain reset without surfacing it.

xezon · 2026-05-30T10:59:19Z

+
+	// TheSuperHackers @refactor bobtista 10/04/2026 Construct the global
+	// IRenderBackend instance now that the D3D device is ready. See
+	// Core/Libraries/Source/WWVegas/WW3D2/RENDER_BACKEND.md.


This comment refers to a file that is not part of the change.

xezon · 2026-05-30T11:00:25Z

+// after the D3D device has been successfully created.
+//
+// Phase 1 always creates a DX8Backend. Phase 2 will add a compile-time
+// option to select between DX8Backend, BgfxBackend, and DiligentBackend.


What is DiligentBackend?

It's another backend like bgfx, I ended up going with bgfx, but if anyone else wants to run with Diligent it would work the same. Cleaned the commit anyway

xezon · 2026-05-30T11:03:32Z

+// Implementations (DX8Backend.cpp, future BgfxBackend.cpp, etc.) can use
+// whatever C++ features the project's main build allows.
+
+class IRenderBackend


How will we cover DX8Caps related stuff?

Capability queries become a set of narrow virtuals with safe defaults eg Supports_Texture_Format(WW3DFormat), Supports_Compressed_Textures(), Get_Texture_Limits(), Supports_Texture_Op(...), etc.

DX8Backend forwards each to DX8Wrapper::Get_Current_Caps(), so DX8Caps stays the reference implementation and is never exposed directly. The few sites that read raw D3DCAPS8 bitfields today (COLORWRITEENABLE in W3DScene/W3DVolumetricShadow, TextureOpCaps in shader.cpp) and the Voodoo3 vendor check get promoted to neutral predicates (Supports_Color_Write_Mask(), Supports_Texture_Op(), Is_Legacy_Voodoo3()) so shared engine code carries no D3D types or #ifdefs. I've kept these out of this scaffolding PR deliberately, each lands with the call-site it unblocks, but the shape is good.

xezon · 2026-05-30T11:04:41Z

+// Implementations (DX8Backend.cpp, future BgfxBackend.cpp, etc.) can use
+// whatever C++ features the project's main build allows.
+
+class IRenderBackend


What will we do with direct calls to DX8, for example _Get_D3D_Device8 or Get_DX8_Texture_Stage_State_Value_Name ?

This took a lot of doing, but has been worth it. In my run ahead branches for bgfx (still local), I have it so there are two classes, handled differently. The high-frequency render/texture-stage-state calls aren't re-exposed as raw D3DRS_/D3DTSS_; they route through a backend-neutral fixed-function state cache (keyed by the same ordinals) plus typed semantic setters, so a non-DX8 backend reads intent rather than D3D enums. The genuinely DX8-only entry points (_Get_D3D_Device8, Create_DX8*, raw SetRenderTarget) migrate to named high-level methods (Set_Render_Target_With_Z, a view-capture primitive, …); the irreducible cases e.g. hand-written water pixel-shader bytecode go behind a named-enum hatch (Create_Legacy_Pixel_Shader(kind)) rather than a raw device pointer. The end state has no _Get_D3D_Device8 left in the engine subsystems; the raw device stays inside DX8Backend. Pure DX8 diagnostics eg Get_DX8_Texture_Stage_State_Value_Name simply stay on DX8Wrapper, as they're debug-only and not part of the abstraction.

xezon · 2026-05-30T11:06:58Z

    proxy.h
    rddesc.h
+    RenderBackend.cpp
+    RenderBackend.h


Can put the backends except IRenderBackend.h into a subfolder so they are tucked away a bit.

I like this, done.

bobtista · 2026-05-31T01:38:59Z

I've already got the bgfx backend working on my Mac and Windows machines, a lot was figured along the way, and some stuff like the lifecycle I'm happy to add here and inherit from. I'm still ironing out some quirks, will share more when things feel polished enough.

greptile-apps · 2026-05-31T01:55:44Z

+	g_renderBackend->Shutdown();
+	Shutdown_Render_Backend();


g_renderBackend->Shutdown() is called unconditionally before Shutdown_Render_Backend(), which contains the null guard. If Do_Onetime_Device_Dependent_Shutdowns() is ever reached without a paired Do_Onetime_Device_Dependent_Inits() — for example through an error-recovery path that resets the device partway through initialization — this is a null-pointer dereference crash. The guard should wrap both calls.

Suggested change

g_renderBackend->Shutdown();

Shutdown_Render_Backend();

if (g_renderBackend != nullptr)

{

g_renderBackend->Shutdown();

}

Shutdown_Render_Backend();

Prompt To Fix With AI

This is a comment left during a code review. Path: Core/Libraries/Source/WWVegas/WW3D2/dx8wrapper.cpp Line: 460-461 Comment: `g_renderBackend->Shutdown()` is called unconditionally before `Shutdown_Render_Backend()`, which contains the null guard. If `Do_Onetime_Device_Dependent_Shutdowns()` is ever reached without a paired `Do_Onetime_Device_Dependent_Inits()` — for example through an error-recovery path that resets the device partway through initialization — this is a null-pointer dereference crash. The guard should wrap both calls. ```suggestion if (g_renderBackend != nullptr) { g_renderBackend->Shutdown(); } Shutdown_Render_Backend(); ``` How can I resolve this? If you propose a fix, please make it concise.

bobtista changed the title ~~feat(ww3d2): add IRenderBackend skeleton (Phase 1, DX8 default)~~ feat(ww3d2): add IRenderBackend Interface Apr 17, 2026

bobtista added 3 commits April 17, 2026 19:40

feat(ww3d2): add IRenderBackend abstract interface

42f2aea

feat(ww3d2): add DX8Backend adapter forwarding to DX8Wrapper statics

97a23e4

feat(ww3d2): add global g_renderBackend pointer and lifecycle wiring

e648a3e

bobtista force-pushed the bobtista/feat/render-backend-interface-skeleton branch 2 times, most recently from 5e014bf to e648a3e Compare April 17, 2026 23:43

TheSuperHackers deleted a comment from greptile-apps Bot Apr 17, 2026

fix(ww3d2): Update copyright headers to TheSuperHackers for new files

1c0f02d

xezon reviewed May 30, 2026

View reviewed changes

bobtista added 3 commits May 31, 2026 11:46

refactor(ww3d2): trim redundant comments from render backend interface

a8f04fa

refactor(ww3d2): move backend implementations into Backend subfolder

987406a

feat(ww3d2): add IRenderBackend Initialize and Shutdown lifecycle hooks

a3d0d92

greptile-apps Bot reviewed May 31, 2026

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bobtista commented Apr 17, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

What this PR adds

Test plan

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Greptile Summary

Confidence Score: 4/5

Important Files Changed

Class Diagram

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bobtista commented May 31, 2026

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bobtista commented Apr 17, 2026 •

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