From 6753fbdfa2911a45a0e80ef2007b0b11958e3e7d Mon Sep 17 00:00:00 2001 From: Mikko Mononen Date: Tue, 2 Jun 2026 16:37:36 +0200 Subject: [PATCH] DrawList: added vertex offset 16-bit ImDrawIdx support for _AddPolyline --- imgui_draw.cpp | 80 ++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 67 insertions(+), 13 deletions(-) diff --git a/imgui_draw.cpp b/imgui_draw.cpp index 90f8714ae..5e1644e13 100644 --- a/imgui_draw.cpp +++ b/imgui_draw.cpp @@ -859,8 +859,8 @@ float ImDrawList::_CalculateCenterBiasedOffset(float thickness) _IdxWritePtr += 3; \ } (void)0 -#define IM_POLYLINE_MITER_ANGLE_LIMIT (-0.9999619f) // cos(179.5) -#define IM_POLYLINE_MITER_LIMIT (4.0f) // ~29 deg +#define IM_POLYLINE_MITER_ANGLE_LIMIT (-0.9999619f) // cos(179.5) +#define IM_POLYLINE_MITER_LIMIT (4.0f) // ~29 deg #define IM_POLYLINE_CONVEX_POLY_MAX_BEVELS (2) // (int)(360/floor(180-29)) // In debug builds the functions are likely not inlined, so inlined check is cheaper. @@ -872,6 +872,41 @@ float ImDrawList::_CalculateCenterBiasedOffset(float thickness) #define IM_IS_TRUNCATED(a) ImIsTruncated(a) #endif +// Called when the current vertex count for a polyline call would overflow the index range. +// Commit the vertices so far, reserve new buffers, reset index, and duplicate the base vertices so that they can be accessed by the new indices. +static void SplitPolyline(ImDrawList* draw_list, int& start_idx_offset, int& start_vtx_offset, int& base_idx) +{ + // Make copy of current base points. + ImDrawVert base0 = draw_list->VtxBuffer.Data[draw_list->_CmdHeader.VtxOffset + base_idx + 0]; + ImDrawVert base1 = draw_list->VtxBuffer.Data[draw_list->_CmdHeader.VtxOffset + base_idx + 1]; + + // Release unused verts and indices. + const int cur_idx_offset = (int)(draw_list->_IdxWritePtr - draw_list->IdxBuffer.Data); + const int cur_vtx_offset = (int)(draw_list->_VtxWritePtr - draw_list->VtxBuffer.Data); + const int remaining_idx_count = draw_list->IdxBuffer.Size - cur_idx_offset; + const int remaining_vtx_count = draw_list->VtxBuffer.Size - cur_vtx_offset; + + IM_ASSERT(remaining_vtx_count >= 0 && remaining_idx_count >= 0); + draw_list->PrimUnreserve(remaining_idx_count, remaining_vtx_count); + + // Reserve remaining verts and indices. + draw_list->PrimReserve(remaining_idx_count, remaining_vtx_count + 2); // +2 for the duplicated base points. + + start_idx_offset = cur_idx_offset; + start_vtx_offset = cur_vtx_offset; + base_idx = (int)draw_list->_VtxCurrentIdx; + + // Duplicate base points + draw_list->_VtxWritePtr[0] = base0; + draw_list->_VtxWritePtr[1] = base1; + draw_list->_VtxWritePtr += 2; + draw_list->_VtxCurrentIdx += 2; +} + +#define IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(new_verts) \ + if (sizeof(ImDrawIdx) == 2 && (Flags & ImDrawListFlags_AllowVtxOffset) && _VtxCurrentIdx + (new_verts) > (1 << 16)) IM_UNLIKELY \ + SplitPolyline(this, start_idx_offset, start_vtx_offset, base_idx) + void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_lengths, const int points_count, ImU32 col, float thickness, ImDrawFlags flags, const ImVec4& tex_uvs, float fringe) { const ImU32 col_trans = col & ~IM_COL32_A_MASK; @@ -924,9 +959,10 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ PrimReserve(idx_count, vtx_count); - ImDrawVert* start_vtx_ptr = _VtxWritePtr; - ImDrawIdx* start_idx_ptr = _IdxWritePtr; - + // These offsets change if we need to create new draw command mid shape. + const int first_vtx_offset = (int)(_VtxWritePtr - VtxBuffer.Data); + int start_vtx_offset = (int)(_VtxWritePtr - VtxBuffer.Data); + int start_idx_offset = (int)(_IdxWritePtr - IdxBuffer.Data); int base_idx = (int)_VtxCurrentIdx; ImVec2 pa, pb, dir; @@ -956,6 +992,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ if (flags & ImDrawFlags_NoAAEnds) { + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(2); + base_idx = (int)_VtxCurrentIdx; IM_APPEND_VTX(p1.x - n1.x * thickness0, p1.y - n1.y * thickness0, uv0, col); IM_APPEND_VTX(p1.x + n1.x * thickness1, p1.y + n1.y * thickness1, uv1, col); @@ -967,6 +1005,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ pb.x = p1.x + dir.x * half_aa; pb.y = p1.y + dir.y * half_aa; + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(4); + base_idx = (int)_VtxCurrentIdx; IM_APPEND_VTX(pa.x - n1.x * thickness0, pa.y - n1.y * thickness0, uv0, col_trans); IM_APPEND_VTX(pa.x + n1.x * thickness1, pa.y + n1.y * thickness1, uv1, col_trans); @@ -989,6 +1029,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ len_sqr1 = sqr_lengths[points_count-1]; // This will be filled later, allocate space. + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(2); + base_idx = (int)_VtxCurrentIdx; IM_APPEND_VTX(0, 0, uv0, col); IM_APPEND_VTX(0, 0, uv1, col); @@ -1012,6 +1054,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ const float miter_offset_y = (n0.y + n1.y) * miter_scale_factor; // Miter + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(2); + const int next_base_idx = (ImDrawIdx)_VtxCurrentIdx; IM_APPEND_VTX(p1.x - miter_offset_x * thickness0, p1.y - miter_offset_y * thickness0, uv0, col); // 2 IM_APPEND_VTX(p1.x + miter_offset_x * thickness1, p1.y + miter_offset_y * thickness1, uv1, col); // 3 @@ -1074,6 +1118,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ // Bevel if (sin_theta < 0.0f) { + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(4); + IM_APPEND_VTX(p1.x - (bn_x + sd_x) * thickness0, p1.y - (bn_y + sd_y) * thickness0, uv0, col); // 2 IM_APPEND_VTX(p1.x, p1.y, uv2, col); // 3 const int next_base_idx = (ImDrawIdx)_VtxCurrentIdx; @@ -1091,6 +1137,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ } else { + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(4); + IM_APPEND_VTX(p1.x + (bn_x + sd_x) * thickness1, p1.y + (bn_y + sd_y) * thickness1, uv1, col); // 2 IM_APPEND_VTX(p1.x, p1.y, uv2, col); // 3 const int next_base_idx = (ImDrawIdx)_VtxCurrentIdx; @@ -1109,6 +1157,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ } else { + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(4); + // Miter const int next_base_idx = (ImDrawIdx)_VtxCurrentIdx; IM_APPEND_VTX(p1.x - miter_offset_x * thickness0, p1.y - miter_offset_y * thickness0, uv0, col); // 2 @@ -1142,6 +1192,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ if (flags & ImDrawFlags_NoAAEnds) { + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(2); + IM_APPEND_VTX(p1.x - n1.x * thickness0, p1.y - n1.y * thickness0, uv0, col); IM_APPEND_VTX(p1.x + n1.x * thickness1, p1.y + n1.y * thickness1, uv1, col); @@ -1156,6 +1208,8 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ pb.x = p1.x + dir.x * half_aa; pb.y = p1.y + dir.y * half_aa; + IM_ADD_POLYLINE_HANDLE_VTX_OFFSET_OVERFLOW(4); + int next_base_idx = (int)_VtxCurrentIdx; IM_APPEND_VTX(pa.x - n1.x * thickness0, pa.y - n1.y * thickness0, uv0, col); IM_APPEND_VTX(pa.x + n1.x * thickness1, pa.y + n1.y * thickness1, uv1, col); @@ -1176,15 +1230,17 @@ void ImDrawList::_AddPolyline(const ImVec2* points, ImVec2* normals, float* sqr_ else { // Connect the path. - start_vtx_ptr[0] = VtxBuffer.Data[_CmdHeader.VtxOffset + base_idx+0]; - start_vtx_ptr[1] = VtxBuffer.Data[_CmdHeader.VtxOffset + base_idx+1]; + VtxBuffer.Data[first_vtx_offset + 0] = VtxBuffer.Data[_CmdHeader.VtxOffset + base_idx+0]; + VtxBuffer.Data[first_vtx_offset + 1] = VtxBuffer.Data[_CmdHeader.VtxOffset + base_idx+1]; } // Restore unused memory - const int vtx_used = (int)(_VtxWritePtr - start_vtx_ptr); - const int idx_used = (int)(_IdxWritePtr - start_idx_ptr); - IM_ASSERT(vtx_used <= vtx_count && idx_used <= idx_count); - PrimUnreserve(idx_count - idx_used, vtx_count - vtx_used); + const int cur_idx_offset = (int)(_IdxWritePtr - IdxBuffer.Data); + const int cur_vtx_offset = (int)(_VtxWritePtr - VtxBuffer.Data); + const int remaining_idx_count = IdxBuffer.Size - cur_idx_offset; + const int remaining_vtx_count = VtxBuffer.Size - cur_vtx_offset; + IM_ASSERT_PARANOID(remaining_idx_count >= 0 && remaining_vtx_count >= 0); + PrimUnreserve(remaining_idx_count, remaining_vtx_count); } static ImU32 ImAlphaMultiply(ImU32 col, float alpha_mul) @@ -1243,8 +1299,6 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32 thickness = _FringeScale; } - // TODO: support splitting very long lines to multiple draw calls. - // Allocate data for temp buffers _Data->TempBuffer.reserve_discard(points_count * 2); ImVec2* normals = _Data->TempBuffer.Data;