[rshapes] Line drawing bug when using Camera2D

[mfbulut]

I tested this on latest commit (commit/52f2a10db610d0e9f619fd7c521db08a876547d0)

Issue description

When using Camera2D Line drawing i want to draw lines from center of the screen to somewhere else here is code i used

Environment

I use Windows 11 with Nvdia graphics card more information below

INFO: GLFW platform: Win32
INFO: PLATFORM: DESKTOP (GLFW): Initialized successfully
INFO: GLAD: OpenGL extensions loaded successfully
INFO: GL: Supported extensions count: 403
INFO: GL: OpenGL device information:
INFO: > Vendor: NVIDIA Corporation
INFO: > Renderer: NVIDIA GeForce RTX 3060 Laptop GPU/PCIe/SSE2
INFO: > Version: 3.3.0 NVIDIA 555.99
INFO: > GLSL: 3.30 NVIDIA via Cg compiler

Issue Screenshot

Code Example

#include "raylib.h"

const char* title = "Title";
const int screenWidth = 1280;
const int screenHeight = 720;
Camera2D camera;

int main()
{
    camera.offset = (Vector2){ screenWidth / 2, screenHeight / 2 };
    camera.target = (Vector2){ 0, 0 };
    camera.rotation = 0.0f;
    camera.zoom = screenHeight / 2.0f;

    SetConfigFlags(FLAG_VSYNC_HINT | FLAG_MSAA_4X_HINT);
    InitWindow(screenWidth, screenHeight, title);

    while (!WindowShouldClose())
    {
        BeginDrawing();
        ClearBackground(BLACK);
        BeginMode2D(camera);

        DrawCircleV((Vector2){0, 0}, 0.1f, WHITE);  // Centered
        DrawLine(0, 0, 0, 1, WHITE);  // Not centered, why?

        EndMode2D();
        EndDrawing();
    }
    CloseWindow();
}

[mfbulut]

Found the source of the issue. Adding 0.5f would center the pixel if using default camera but when using a diffrent camera it causes some issues.

void DrawLine(int startPosX, int startPosY, int endPosX, int endPosY, Color color)
{
    rlBegin(RL_LINES);
        rlColor4ub(color.r, color.g, color.b, color.a);
        // WARNING: Adding 0.5f offset to "center" point on selected pixel
        rlVertex2f((float)startPosX + 0.5f, (float)startPosY + 0.5f);
        rlVertex2f((float)endPosX + 0.5f, (float)endPosY + 0.5f);
    rlEnd();
}

Potential fixes:

1. Remove 0.5f offset return to old version (does it really matter);
2. Divide 0.5f with camera's zoom level

[raysan5]

@mfbulut Oh! Good catch! Reviewing it!