AddLineMultiColor

[PhillipDaPaster]

Added AddLineMultiColor to the api since i saw there way no gradient lines naturally supported

void DrawGradientCircle(ImDrawList* draw, const ImVec2& center, float radius, int segments, float thickness) {
    for (int i = 0; i < segments; i++) {
        float theta1 = (2.0f * IM_PI * i) / segments;
        float theta2 = (2.0f * IM_PI * (i + 1)) / segments;

        ImVec2 p1(center.x + cosf(theta1) * radius, center.y + sinf(theta1) * radius);
        ImVec2 p2(center.x + cosf(theta2) * radius, center.y + sinf(theta2) * radius);

        ImU32 col_start = IM_COL32(
            (int)((cosf(theta1) * 0.5f + 0.5f) * 255),
            (int)((sinf(theta1) * 0.5f + 0.5f) * 255),
            (int)((cosf(theta1 + IM_PI / 2) * 0.5f + 0.5f) * 255),
            255
        );

        ImU32 col_end = IM_COL32(
            (int)((cosf(theta2) * 0.5f + 0.5f) * 255),
            (int)((sinf(theta2) * 0.5f + 0.5f) * 255),
            (int)((cosf(theta2 + IM_PI / 2) * 0.5f + 0.5f) * 255),
            255
        );

        draw->AddLineMultiColor(p1, p2, col_start, col_end, thickness);
    }
}

void DrawSpiral(ImDrawList* draw, const ImVec2& center, float radius, int segments, float turns, float thickness) {
    for (int i = 0; i < segments; i++) {
        float t1 = (float)i / segments;
        float t2 = (float)(i + 1) / segments;

        float angle1 = 2.0f * IM_PI * turns * t1;
        float angle2 = 2.0f * IM_PI * turns * t2;

        float r1 = t1 * radius;
        float r2 = t2 * radius;

        ImVec2 p1(center.x + cosf(angle1) * r1, center.y + sinf(angle1) * r1);
        ImVec2 p2(center.x + cosf(angle2) * r2, center.y + sinf(angle2) * r2);

        ImU32 col_start = IM_COL32((int)(t1 * 255), 0, (int)((1 - t1) * 255), 255);
        ImU32 col_end = IM_COL32((int)(t2 * 255), 0, (int)((1 - t2) * 255), 255);

        draw->AddLineMultiColor(p1, p2, col_start, col_end, thickness);
    }
}

void DrawRays(ImDrawList* draw, const ImVec2& center, int rays, float length, float thickness) {
    for (int i = 0; i < rays; i++) {
        float theta = (2.0f * IM_PI * i) / rays;

        ImVec2 p1 = center;
        ImVec2 p2(center.x + cosf(theta) * length, center.y + sinf(theta) * length);

        ImU32 col_start = IM_COL32(255, 255, 0, 255); 
        ImU32 col_end = IM_COL32(255, 0, 0, 0);     

        draw->AddLineMultiColor(p1, p2, col_start, col_end, thickness);
    }
}

void DrawWave(ImDrawList* draw, const ImVec2& start, float length, float amplitude, int points, float thickness) {
    for (int i = 0; i < points; i++) {
        float t1 = (float)i / points;
        float t2 = (float)(i + 1) / points;

        ImVec2 p1(start.x + t1 * length, start.y + sinf(t1 * 4 * IM_PI) * amplitude);
        ImVec2 p2(start.x + t2 * length, start.y + sinf(t2 * 4 * IM_PI) * amplitude);

        ImU32 col_start = IM_COL32((int)(t1 * 255), (int)((1 - t1) * 255), 128, 255);
        ImU32 col_end = IM_COL32((int)(t2 * 255), (int)((1 - t2) * 255), 128, 255);

        draw->AddLineMultiColor(p1, p2, col_start, col_end, thickness);
    }
}

 ImGui::Begin("Example");

 ImGuiWindow* window = ImGui::GetCurrentWindow();
 ImDrawList* draw = window->DrawList;
 draw->Flags |= ImDrawListFlags_AntiAliasedLines;

 ImVec2 pos = ImGui::GetCursorScreenPos();

 DrawGradientCircle(draw, ImVec2(pos.x + 150, pos.y + 150), 100.0f, 128, 6.0f);
 DrawSpiral(draw, ImVec2(pos.x + 500, pos.y + 150), 80.0f, 200, 3.0f, 3.0f);
 DrawRays(draw, ImVec2(pos.x + 150, pos.y + 500), 32, 100.0f, 4.0f);
 DrawWave(draw, ImVec2(pos.x + 350, pos.y + 450), 300.0f, 40.0f, 200, 3.0f);

 ImGui::End();

[ocornut]

Thank you Philipp for your PR.

The main problem with this approach are that lines are not anti-aliased. So for now I'd suggest you use this in your code as a standalone function.

I think once we merge #7972 #2964 we can consider providing a version where a color is submitted per vertex, and then it becomes trivial to provide a AddLineMultiColor().

[PhillipDaPaster]

all good i kinda just coded it well enough to work for my use case but looking foward to that drawlist update