sacred_k/src/game/ui/draw.h

#pragma once
// Untextured quads on the UI's Direct3D 7 device (the argument of the UI's
// render methods, vf14).

#include <cstdint>

#include <windows.h>

namespace game {

constexpr int kDeviceDrawPrimitive = 25;  // IDirect3DDevice7 vtable slots
constexpr int kDeviceSetTexture = 35;
constexpr int kDeviceSetRenderState = 20;
constexpr int kDeviceGetRenderState = 21;
constexpr DWORD kStateSourceBlend = 19;  // D3DRENDERSTATETYPE
constexpr DWORD kStateDestinationBlend = 20;
constexpr DWORD kStateAlphaBlendEnable = 27;
constexpr DWORD kBlendOne = 2;  // D3DBLEND
constexpr DWORD kTriangleStrip = 5;
constexpr DWORD kFvfScreenColourTexture = 0x1c4;  // XYZRHW | DIFFUSE | SPECULAR | TEX1

struct ScreenVertex {
    float x, y, z, rhw;
    uint32_t diffuse, specular;
    float u, v;
};

// Draws (x0, y0)-(x1, y1) with `surface` (a texture's Direct3D surface,
// game/ui/texture.h) from (u0, v0) to (u1, v1), tinted by `colour`.
inline void DrawTextured(void* device, void* surface, float x0, float y0, float x1, float y1, float u0, float v0,
                         float u1, float v1, uint32_t colour = 0xffffffff) {
    void** vtable = *static_cast<void***>(device);
    using SetTextureFn = HRESULT(__stdcall*)(void*, DWORD, void*);
    using DrawPrimitiveFn = HRESULT(__stdcall*)(void*, DWORD, DWORD, void*, DWORD, DWORD);
    reinterpret_cast<SetTextureFn>(vtable[kDeviceSetTexture])(device, 0, surface);
    ScreenVertex quad[4] = {{x0, y0, 0, 1, colour, 0, u0, v0},
                            {x1, y0, 0, 1, colour, 0, u1, v0},
                            {x0, y1, 0, 1, colour, 0, u0, v1},
                            {x1, y1, 0, 1, colour, 0, u1, v1}};
    reinterpret_cast<DrawPrimitiveFn>(vtable[kDeviceDrawPrimitive])(device, kTriangleStrip, kFvfScreenColourTexture,
                                                                     quad, 4, 0);
    reinterpret_cast<SetTextureFn>(vtable[kDeviceSetTexture])(device, 0, nullptr);
}

// DrawTextured added onto what is drawn (source and destination blend ONE):
// for the effect textures, drawn on black without alpha.
inline void DrawTexturedAdded(void* device, void* surface, float x0, float y0, float x1, float y1, float u0,
                              float v0, float u1, float v1) {
    void** vtable = *static_cast<void***>(device);
    using SetRenderStateFn = HRESULT(__stdcall*)(void*, DWORD, DWORD);
    using GetRenderStateFn = HRESULT(__stdcall*)(void*, DWORD, DWORD*);
    const auto set = reinterpret_cast<SetRenderStateFn>(vtable[kDeviceSetRenderState]);
    const auto get = reinterpret_cast<GetRenderStateFn>(vtable[kDeviceGetRenderState]);
    DWORD blending = 0, source = 0, destination = 0;
    get(device, kStateAlphaBlendEnable, &blending);
    get(device, kStateSourceBlend, &source);
    get(device, kStateDestinationBlend, &destination);
    set(device, kStateAlphaBlendEnable, TRUE);
    set(device, kStateSourceBlend, kBlendOne);
    set(device, kStateDestinationBlend, kBlendOne);
    DrawTextured(device, surface, x0, y0, x1, y1, u0, v0, u1, v1);
    set(device, kStateAlphaBlendEnable, blending);
    set(device, kStateSourceBlend, source);
    set(device, kStateDestinationBlend, destination);
}

// Fills (x0, y0)-(x1, y1), ARGB colours per corner: top left, top right,
// bottom left, bottom right (blended between them).
inline void FillCorners(void* device, float x0, float y0, float x1, float y1, uint32_t topLeft, uint32_t topRight,
                        uint32_t bottomLeft, uint32_t bottomRight) {
    void** vtable = *static_cast<void***>(device);
    using SetTextureFn = HRESULT(__stdcall*)(void*, DWORD, void*);
    using DrawPrimitiveFn = HRESULT(__stdcall*)(void*, DWORD, DWORD, void*, DWORD, DWORD);
    reinterpret_cast<SetTextureFn>(vtable[kDeviceSetTexture])(device, 0, nullptr);
    ScreenVertex quad[4] = {{x0, y0, 0, 1, topLeft, 0, 0, 0},
                            {x1, y0, 0, 1, topRight, 0, 1, 0},
                            {x0, y1, 0, 1, bottomLeft, 0, 0, 1},
                            {x1, y1, 0, 1, bottomRight, 0, 1, 1}};
    reinterpret_cast<DrawPrimitiveFn>(vtable[kDeviceDrawPrimitive])(device, kTriangleStrip, kFvfScreenColourTexture,
                                                                     quad, 4, 0);
}

// Untextured triangles, three vertices each (a triangle list), in batches the
// device takes in one call.
inline void FillTriangles(void* device, ScreenVertex* vertices, size_t count) {
    constexpr DWORD kTriangleList = 4;
    constexpr size_t kBatch = 3 * 10000;
    void** vtable = *static_cast<void***>(device);
    using SetTextureFn = HRESULT(__stdcall*)(void*, DWORD, void*);
    using DrawPrimitiveFn = HRESULT(__stdcall*)(void*, DWORD, DWORD, void*, DWORD, DWORD);
    reinterpret_cast<SetTextureFn>(vtable[kDeviceSetTexture])(device, 0, nullptr);
    for (size_t first = 0; first < count; first += kBatch) {
        const size_t batch = count - first < kBatch ? count - first : kBatch;
        reinterpret_cast<DrawPrimitiveFn>(vtable[kDeviceDrawPrimitive])(
            device, kTriangleList, kFvfScreenColourTexture, vertices + first, static_cast<DWORD>(batch), 0);
    }
}

// Fills (x0, y0)-(x1, y1) with the ARGB colour `color`.
inline void FillRect(void* device, float x0, float y0, float x1, float y1, uint32_t color) {
    FillCorners(device, x0, y0, x1, y1, color, color, color, color);
}

// Top to bottom from `top` to `bottom`.
inline void FillVertical(void* device, float x0, float y0, float x1, float y1, uint32_t top, uint32_t bottom) {
    FillCorners(device, x0, y0, x1, y1, top, top, bottom, bottom);
}

// Left to right from `left` to `right`.
inline void FillHorizontal(void* device, float x0, float y0, float x1, float y1, uint32_t left, uint32_t right) {
    FillCorners(device, x0, y0, x1, y1, left, right, left, right);
}

} // namespace game