#if SPECIAL
#include "main.h"
#endif


static real32
Bezier_SolveYForX(v2 Point_P0, v2 Point_P1, v2 Point_P2, v2 Point_P3, real32 TargetX) {

    real32 Y = 0;

    v2 m1 = (Point_P2 - Point_P0) / (2 * Tau);
    v2 m2 = (Point_P3 - Point_P1) / (2 * Tau);

    real32 Precision = 0.000001;
    real32 t = (TargetX - Point_P0.x) / (Point_P3.x - Point_P0.x);

    int Iterations = 0;
    for (;;) {
        real32 t2 = t * t;
        real32 t3 = t2 * t;
        real32 mt = 1-t;
        real32 mt2 = mt * mt;
        real32 mt3 = mt2 * mt;
        v2 Point = (Point_P0 * mt3) + (3 * Point_P1 * mt2 * t) + (3 * Point_P2 * mt * t2) + (Point_P3 * t3);

        bool32 Cond1 = (Point.x <= (TargetX - Precision));
        bool32 Cond2 = (Point.x >= (TargetX + Precision));

        if ((Cond1 || Cond2) && Iterations < 10) {
            t = t * TargetX / Point.x;
            Iterations++;
        } else {
            Y = Point.y;
            break;
        }
    }

    return Y;
}

// All the extra inputs on the second line are for when we need to take
// interactive mode into account.
// TODO(fox): Incorporate sorting for non-continuous shapes.
static uint32
Bezier_Shape_Sort(memory *Memory, shape_layer *Shape, bezier_point *PointData,
                  project_state *State, layer_transforms T, int Width, int Height,
                  int CompWidth, int CompHeight, real32 Radius, bool32 Interact)
{
    bezier_point *PointStart = PointData;
    for (int i = 0; i < Shape->Point_Count; i++) {
        bezier_point Point = *Bezier_LookupAddress(Memory, Shape->Block_Bezier_Index, i, 1);
        if (Width != 0 && Height != 0) {
            for (int a = 0; a < 3; a++) {
                Point.Pos[a] = Point.Pos[a] * V2(Width, Height);
            }
        }
        if (State->Interact_Active == interact_type_keyframe_move && Interact && Point.IsSelected) {
            v2 Pos = Point.Pos[0];
            Pos = TransformPoint(T, Width, Height, Pos);
            Pos.x += State->Interact_Offset[0];
            Pos.y += State->Interact_Offset[1];
            Pos = T_CompPosToLayerPos(T, CompWidth, CompHeight, Width, Height, Pos.x, Pos.y);
            Point.Pos[0] = Pos;
        }
        // Corner rounder
        if ((Radius > 0 && Point.Type == interpolation_type_linear) &&
            (Shape->IsClosed || (i != 0 && i != (Shape->Point_Count - 1)) )) {
            v2 Pos = Point.Pos[0];
            int Index_Prev = (i != 0) ? i-1 : Shape->Point_Count-1;
            int Index_Next = (i != Shape->Point_Count-1) ? i+1 : 0;
            bezier_point *Point_Prev = Bezier_LookupAddress(Memory, Shape->Block_Bezier_Index, Index_Prev, 1);
            bezier_point *Point_Next = Bezier_LookupAddress(Memory, Shape->Block_Bezier_Index, Index_Next, 1);
            v2 Pos_Prev = Point_Prev->Pos[0];
            v2 Pos_Next = Point_Next->Pos[0];
            if (Width != 0 && Height != 0) {
                    Pos_Prev = Pos_Prev * V2(Width, Height);
                    Pos_Next = Pos_Next * V2(Width, Height);
            }
            // TODO(fox): debloat
            if (State->Interact_Active == interact_type_keyframe_move && Interact && Point_Prev->IsSelected) {
                v2 Pos = Pos_Prev;
                Pos = TransformPoint(T, Width, Height, Pos);
                Pos.x += State->Interact_Offset[0];
                Pos.y += State->Interact_Offset[1];
                Pos = T_CompPosToLayerPos(T, CompWidth, CompHeight, Width, Height, Pos.x, Pos.y);
                Pos_Prev = Pos;
            }
            if (State->Interact_Active == interact_type_keyframe_move && Interact && Point_Next->IsSelected) {
                v2 Pos = Pos_Next;
                Pos = TransformPoint(T, Width, Height, Pos);
                Pos.x += State->Interact_Offset[0];
                Pos.y += State->Interact_Offset[1];
                Pos = T_CompPosToLayerPos(T, CompWidth, CompHeight, Width, Height, Pos.x, Pos.y);
                Pos_Next = Pos;
            }
            v2 Vector_Prev = Pos - Pos_Prev;
            v2 Vector_Next = Pos - Pos_Next;
            real32 Length_Prev = sqrtf(LengthSq(Vector_Prev));
            real32 Length_Next = sqrtf(LengthSq(Vector_Next));

            // real32 RadAngle = acos(Inner(Vector_Prev, VectorR) / (LengthL * LengthR)) * PI / 180;
            // real32 AngleKappa = (4.f/3) * tan(RadAngle * 1/4);

            real32 Ratio_Prev = Min(Radius / Length_Prev, 0.5);
            real32 Ratio_Prev_Inv = 1.0f - Ratio_Prev;

            real32 Ratio_Next = Min(Radius / Length_Next, 0.5);
            real32 Ratio_Next_Inv = 1.0f - Ratio_Next;

            v2 Point_1 = Pos_Prev + V2(Vector_Prev.x * Ratio_Prev_Inv, (Vector_Prev.y * Ratio_Prev_Inv));
            v2 Point_2 = Vector_Prev * Ratio_Prev * (1-KAPPA);
            v2 Point_3 = Pos_Next + V2(Vector_Next.x * Ratio_Next_Inv, Vector_Next.y * Ratio_Next_Inv);
            v2 Point_4 = Vector_Next * Ratio_Next * (1-KAPPA);

            *PointData++ = { 1, { Point_1, Point_2, V2(0, 0) }, interpolation_type_bezier, Point.IsSelected };
            *PointData++ = { 1, { Point_3, V2(0, 0), Point_4 }, interpolation_type_bezier, Point.IsSelected };
        } else {
            *PointData++ = Point;
        }
    }
    return PointData - PointStart;
}

static bezier_point *
Bezier_LookupAddress(memory *Memory, uint16 *Block_Bezier_Index, uint16 Index, bool32 AssertExists)
{
    Assert(Index < (MAX_KEYFRAMES_PER_BLOCK * MAX_KEYFRAME_BLOCKS));
    int SeekBlock = Index / MAX_KEYFRAMES_PER_BLOCK;
    int SeekIndex = Index - (SeekBlock * MAX_KEYFRAMES_PER_BLOCK);
    block_bezier *Bezier = (block_bezier *)Memory_Block_AddressAtIndex(Memory, F_Bezier, Block_Bezier_Index[SeekBlock], 0);
    Assert(Bezier->Occupied);
    if (AssertExists)
        Assert(Bezier->Point[SeekIndex].Occupied);
    return &Bezier->Point[SeekIndex];
}

static void
Bezier_Interact_Evaluate(project_state *State, bezier_point *PointAddress, v2 *Pos, real32 GraphZoomHeight, real32 Y_Increment)
{
    Pos[0] = PointAddress->Pos[0];
    Pos[1] = PointAddress->Pos[1];
    Pos[2] = PointAddress->Pos[2];
    if (PointAddress->IsSelected) {
        if (State->Interact_Active == interact_type_keyframe_move) {
            if (State->Interact_Modifier != 2)
                Pos[PointAddress->IsSelected - 1].x += (int32)State->Interact_Offset[0];
            if (State->Interact_Modifier != 1)
                Pos[PointAddress->IsSelected - 1].y -= (State->Interact_Offset[1] / GraphZoomHeight / Y_Increment);
        } else if (State->Interact_Active == interact_type_keyframe_scale) {
            Pos[1].x += State->Interact_Offset[0];
            Pos[2].x -= State->Interact_Offset[0];
        } else if (State->Interact_Active == interact_type_keyframe_rotate) {
            // how do I do this??
            Assert(0);
        }
    }
}

static void
Bezier_Add(memory *Memory, memory_table_list TableName, uint16 *Block_Bezier_Index, uint16 *Block_Bezier_Count,
           uint16 *PointCount, bezier_point PointData)
{
    int k = 0;
    for (;;) {
        int SeekBlock = k / MAX_KEYFRAMES_PER_BLOCK;
        if ((SeekBlock + 1) > *Block_Bezier_Count) {
            Block_Bezier_Index[SeekBlock] = Memory_Block_AllocateNew(Memory, F_Bezier);
            block_bezier *Bezier = (block_bezier *)Memory_Block_AddressAtIndex(Memory, F_Bezier, Block_Bezier_Index[SeekBlock], 0);
            Bezier->Occupied = true;
            History_Action_Swap(Memory, TableName, sizeof(*Block_Bezier_Count), Block_Bezier_Count);
            *Block_Bezier_Count += 1;
        }
        bezier_point *Point = Bezier_LookupAddress(Memory, Block_Bezier_Index, k, 0);
        if (!Point->Occupied) {
            History_Action_Swap(Memory, F_Bezier, sizeof(*Point), Point);
            *Point = PointData;
            History_Action_Swap(Memory, TableName, sizeof(*PointCount), PointCount);
            *PointCount += 1;
            return;
        }
        k++;
    }
}

static void
Bezier_Delete(memory *Memory, memory_table_list TableName, uint16 *Block_Bezier_Index, uint16 *PointCount, uint16 *ArrayLocation)
{
    for (int p = 0; p < *PointCount; p++) {
        int k = ArrayLocation[p];
        bezier_point *Point = Bezier_LookupAddress(Memory, Block_Bezier_Index, k);
        if (Point->IsSelected) {
            History_Action_Swap(Memory, F_Bezier, sizeof(Point->Occupied), &Point->Occupied);
            Point->Occupied = 0;
            History_Action_Swap(Memory, TableName, sizeof(*PointCount), PointCount);
            *PointCount -= 1;
        }
    }
}

static int32
Bezier_CheckSameX(memory *Memory, memory_table_list TableName, uint16 *Block_Bezier_Index, uint16 KeyframeCount, uint16 *ArrayLocation, real32 ValX)
{
    for (int p = 0; p < KeyframeCount; p++) {
        int k = ArrayLocation[p];
        bezier_point *Point = Bezier_LookupAddress(Memory, Block_Bezier_Index, k);
        if (Point->Pos[0].x == ValX) {
            return k;
        }
    }
    return -1;
}

// return all points
static void Bezier_CubicCalcPointsCasteljauStep(void *Data, uint32 Size, uint32 *Increment, real32 x1, real32 y1, real32 x2, real32 y2, real32 x3, real32 y3, real32 x4, real32 y4, real32 tess_tol, int level)
{
    real32 dx = x4 - x1;
    real32 dy = y4 - y1;
    real32 d2 = ((x2 - x4) * dy - (y2 - y4) * dx);
    real32 d3 = ((x3 - x4) * dy - (y3 - y4) * dx);
    d2 = (d2 >= 0) ? d2 : -d2;
    d3 = (d3 >= 0) ? d3 : -d3;
    if ((d2 + d3) * (d2 + d3) < tess_tol * (dx * dx + dy * dy))
    {
        real32 *Address = (real32 *)((uint8 *)Data + *Increment*Size);
        *Address = x4;
        *(Address + 1) = y4;
        *(Address + 2) = 0;
        *Increment += 1;
    }
    else if (level < 10)
    {
        real32 x12 = (x1 + x2)*0.5f,       y12 = (y1 + y2)*0.5f;
        real32 x23 = (x2 + x3)*0.5f,       y23 = (y2 + y3)*0.5f;
        real32 x34 = (x3 + x4)*0.5f,       y34 = (y3 + y4)*0.5f;
        real32 x123 = (x12 + x23)*0.5f,    y123 = (y12 + y23)*0.5f;
        real32 x234 = (x23 + x34)*0.5f,    y234 = (y23 + y34)*0.5f;
        real32 x1234 = (x123 + x234)*0.5f, y1234 = (y123 + y234)*0.5f;
        Bezier_CubicCalcPointsCasteljauStep(Data, Size, Increment, x1, y1, x12, y12, x123, y123, x1234, y1234, tess_tol, level + 1);
        Bezier_CubicCalcPointsCasteljauStep(Data, Size, Increment, x1234, y1234, x234, y234, x34, y34, x4, y4, tess_tol, level + 1);
    }
}

void * Bezier_CubicCalcPoints(v2 p1, v2 p2, v2 p3, v2 p4, void *Data, uint32 Size)
{
    uint32 Increment = 0;
    real32 tess_tol = TESS_TOL;
    void *Pointer = Data;
    Bezier_CubicCalcPointsCasteljauStep(Pointer, Size, &Increment, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y, tess_tol, 0);
    return ((uint8 *)Data + (Increment * Size));
}

v2 Bezier_LineDist(v2 a, v2 b, v2 p)
{
    v2 ap = p - a;
    v2 ab_dir = b - a;
    real32 dot = ap.x * ab_dir.x + ap.y * ab_dir.y;
    if (dot < 0.0f) {
        return a;
    }
    real32 ab_len_sqr = ab_dir.x * ab_dir.x + ab_dir.y * ab_dir.y;
    if (dot > ab_len_sqr) {
        return b;
    }
    return p - (a + ab_dir * dot / ab_len_sqr);
}

v2 Bezier_LineClosestPoint(v2 a, v2 b, v2 p)
{
    v2 ap = p - a;
    v2 ab_dir = b - a;
    real32 dot = ap.x * ab_dir.x + ap.y * ab_dir.y;
    if (dot < 0.0f) {
        return a;
    }
    real32 ab_len_sqr = ab_dir.x * ab_dir.x + ab_dir.y * ab_dir.y;
    if (dot > ab_len_sqr) {
        return b;
    }
    return a + ab_dir * dot / ab_len_sqr;
}

// The ratio here is just the dot product divided by the squared length.
v2 Bezier_LineClosestPointR(v2 a, v2 b, v2 p, real32 *ratio)
{
    v2 ap = p - a;
    v2 ab_dir = b - a;
    real32 dot = ap.x * ab_dir.x + ap.y * ab_dir.y;
    if (dot < 0.0f) {
        *ratio = 0.0f;
        return a;
    }
    real32 ab_len_sqr = ab_dir.x * ab_dir.x + ab_dir.y * ab_dir.y;
    if (dot > ab_len_sqr) {
        *ratio = 1.0f;
        return b;
    }
    *ratio = dot / ab_len_sqr;
    return a + ab_dir * dot / ab_len_sqr;
}

static void Bezier_CubicBoxCasteljauStep(v2 Min, v2 Max, v2 *p_closest, v2 *p_last, real32 *p_closest_dist2,
                                                    real32 x1, real32 y1, real32 x2, real32 y2, real32 x3, real32 y3, real32 x4, real32 y4, real32 tess_tol, int level)
{
    real32 dx = x4 - x1;
    real32 dy = y4 - y1;
    real32 d2 = ((x2 - x4) * dy - (y2 - y4) * dx);
    real32 d3 = ((x3 - x4) * dy - (y3 - y4) * dx);
    d2 = (d2 >= 0) ? d2 : -d2;
    d3 = (d3 >= 0) ? d3 : -d3;
    if ((d2 + d3) * (d2 + d3) < tess_tol * (dx * dx + dy * dy))
    {
        v2 p_current = V2(x4, y4);
        v2 p[4] = { Min, Max, V2(Min.x, Max.y), V2(Max.y, Min.x) };
        for (int i = 0; i < 4; i++) {
            v2 p_line = Bezier_LineClosestPoint(*p_last, p_current, p[i]);
            real32 dist2 = LengthSq(p[i] - p_line);
            if (dist2 < p_closest_dist2[i])
            {
                p_closest[i] = p_line;
                p_closest_dist2[i] = dist2;
            }
        }
        *p_last = p_current;
    }
    else if (level < 10)
    {
        real32 x12 = (x1 + x2)*0.5f,       y12 = (y1 + y2)*0.5f;
        real32 x23 = (x2 + x3)*0.5f,       y23 = (y2 + y3)*0.5f;
        real32 x34 = (x3 + x4)*0.5f,       y34 = (y3 + y4)*0.5f;
        real32 x123 = (x12 + x23)*0.5f,    y123 = (y12 + y23)*0.5f;
        real32 x234 = (x23 + x34)*0.5f,    y234 = (y23 + y34)*0.5f;
        real32 x1234 = (x123 + x234)*0.5f, y1234 = (y123 + y234)*0.5f;
        Bezier_CubicBoxCasteljauStep(Min, Max, p_closest, p_last, p_closest_dist2, x1, y1, x12, y12, x123, y123, x1234, y1234, tess_tol, level + 1);
        Bezier_CubicBoxCasteljauStep(Min, Max, p_closest, p_last, p_closest_dist2, x1234, y1234, x234, y234, x34, y34, x4, y4, tess_tol, level + 1);
    }
}

static void
Bezier_BoxTest(v2 p1, v2 p2, v2 p3, v2 p4, v2 Min, v2 Max, v2 *p_closest)
{
    real32 tess_tol = TESS_TOL;
    v2 p_last = p1;
    real32 p_closest_dist2[4] = { FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX };
    Bezier_CubicBoxCasteljauStep(Min, Max, p_closest, &p_last, p_closest_dist2, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y, tess_tol, 0);
}


#if 0
// Following the algorithm, we take the ratio from the _leftmost_ point in each
// subdivision of the cubic spline until we're within tess_tol, and then we
// interpolate it with the subdivision's rightmost point in the ClosestPoint call.
// The pow(0.5, level) represents the ratio of the next subdivision's leftmost
// point (AKA the rightmost point of the current subdivision).

// finds the point closest to p and also fills out its ratio along the curve
static void Bezier_CubicClosestPointCasteljauStep(v2 p, v2 *p_closest, real32 ratio, real32 *r_closest, v2 *p_last, real32 *p_closest_dist2,
                                                    real32 x1, real32 y1, real32 x2, real32 y2, real32 x3, real32 y3, real32 x4, real32 y4, real32 tess_tol, int level)
{
    real32 dx = x4 - x1;
    real32 dy = y4 - y1;
    real32 d2 = ((x2 - x4) * dy - (y2 - y4) * dx);
    real32 d3 = ((x3 - x4) * dy - (y3 - y4) * dx);
    d2 = (d2 >= 0) ? d2 : -d2;
    d3 = (d3 >= 0) ? d3 : -d3;
    if ((d2 + d3) * (d2 + d3) < tess_tol * (dx * dx + dy * dy))
    {
        v2 p_current = V2(x4, y4);
        real32 added_ratio;
        v2 p_line = Bezier_LineClosestPoint(*p_last, p_current, p, &added_ratio);
        real32 dist2 = LengthSq(p - p_line);
        if (dist2 < *p_closest_dist2)
        {
            *p_closest = p_line;
            *p_closest_dist2 = dist2;
            *r_closest = ratio + pow(0.5, level)*added_ratio;
        }
        *p_last = p_current;
    }
    else if (level < 10)
    {
        real32 x12 = (x1 + x2)*0.5f,       y12 = (y1 + y2)*0.5f;
        real32 x23 = (x2 + x3)*0.5f,       y23 = (y2 + y3)*0.5f;
        real32 x34 = (x3 + x4)*0.5f,       y34 = (y3 + y4)*0.5f;
        real32 x123 = (x12 + x23)*0.5f,    y123 = (y12 + y23)*0.5f;
        real32 x234 = (x23 + x34)*0.5f,    y234 = (y23 + y34)*0.5f;
        real32 x1234 = (x123 + x234)*0.5f, y1234 = (y123 + y234)*0.5f;
        Bezier_CubicClosestPointCasteljauStep(p, p_closest, ratio, r_closest, p_last, p_closest_dist2, x1, y1, x12, y12, x123, y123, x1234, y1234, tess_tol, level + 1);
        Bezier_CubicClosestPointCasteljauStep(p, p_closest, ratio + pow(0.5, level+1), r_closest, p_last, p_closest_dist2, x1234, y1234, x234, y234, x34, y34, x4, y4, tess_tol, level + 1);
    }
}

real32 Bezier_CubicRatioOfPoint(v2 p1, v2 p2, v2 p3, v2 p4, v2 p)
{
    real32 tess_tol = TESS_TOL;
    v2 p_last = p1;
    v2 p_closest;
    real32 p_closest_dist2 = FLT_MAX;
    real32 ratio = 0;
    Bezier_CubicClosestPointCasteljauStep(p, &p_closest, 0, &ratio, &p_last, &p_closest_dist2, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y, tess_tol, 0);
    return ratio;
}
#endif


#if 0
// A modified version of the bezier code in ImGui with extra features for bitmap and path interaction.

// Function to convert a ratio back into a point for the bezier handles.
v2 Line_RatioToPoint(v2 a, v2 b, real32 ratio)
{
    v2 ab_dir = b - a;
    real32 ab_len_sqr = ab_dir.x * ab_dir.x + ab_dir.y * ab_dir.y;
    real32 dot = ratio*ab_len_sqr;
    return a + ab_dir * dot / V2(ab_len_sqr);
}

// finds the min/max bounds of the curve
static void Bezier_CubicMinMaxCasteljauStep(v2 *p_min, v2 *p_max, real32 x1, real32 y1, real32 x2, real32 y2, real32 x3, real32 y3, real32 x4, real32 y4, real32 tess_tol, int level)
{
    real32 dx = x4 - x1;
    real32 dy = y4 - y1;
    real32 d2 = ((x2 - x4) * dy - (y2 - y4) * dx);
    real32 d3 = ((x3 - x4) * dy - (y3 - y4) * dx);
    d2 = (d2 >= 0) ? d2 : -d2;
    d3 = (d3 >= 0) ? d3 : -d3;
    if ((d2 + d3) * (d2 + d3) < tess_tol * (dx * dx + dy * dy))
    {
        v2 p_current = V2(x4, y4);
        if (p_current.x < p_min->x) {
            p_min->x = p_current.x;
        }
        if (p_current.y < p_min->y) {
            p_min->y = p_current.y;
        }
        if (p_current.x > p_max->x) {
            p_max->x = p_current.x;
        }
        if (p_current.y > p_max->y) {
            p_max->y = p_current.y;
        }
    }
    else if (level < 10)
    {
        real32 x12 = (x1 + x2)*0.5f,       y12 = (y1 + y2)*0.5f;
        real32 x23 = (x2 + x3)*0.5f,       y23 = (y2 + y3)*0.5f;
        real32 x34 = (x3 + x4)*0.5f,       y34 = (y3 + y4)*0.5f;
        real32 x123 = (x12 + x23)*0.5f,    y123 = (y12 + y23)*0.5f;
        real32 x234 = (x23 + x34)*0.5f,    y234 = (y23 + y34)*0.5f;
        real32 x1234 = (x123 + x234)*0.5f, y1234 = (y123 + y234)*0.5f;
        Bezier_CubicMinMaxCasteljauStep(p_min, p_max, x1, y1, x12, y12, x123, y123, x1234, y1234, tess_tol, level + 1);
        Bezier_CubicMinMaxCasteljauStep(p_min, p_max, x1234, y1234, x234, y234, x34, y34, x4, y4, tess_tol, level + 1);
    }
}

real32 Bezier_CubicRatioOfPoint(v2 p1, v2 p2, v2 p3, v2 p4, v2 p)
{
    real32 tess_tol = TESS_TOL;
    v2 p_last = p1;
    v2 p_closest;
    real32 p_closest_dist2 = FLT_MAX;
    real32 ratio = 0;
    Bezier_CubicClosestPointCasteljauStep(p, &p_closest, 0, &ratio, &p_last, &p_closest_dist2, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y, tess_tol, 0);
    return ratio;
}

// These functions will become more generalized as shapes are added.

static void
Mask_AddPointToLine(mask *Mask, uint16 Index, v2 Pos)
{
    for (int i = Mask->NumberOfPoints - 1; i > Index; i--) {
        Mask->Point[i+1] = Mask->Point[i];
    }
    mask_point *PointToAdd = &Mask->Point[Index+1];
    PointToAdd->Pos = Pos;
    Mask->NumberOfPoints++;
}

static void
Mask_PushPoint(mask *Mask, v2 Pos)
{
    mask_point *PointToAdd = &Mask->Point[Mask->NumberOfPoints];
    PointToAdd->Pos = Pos;
    Mask->NumberOfPoints++;
}

static void
Mask_ShiftPointers(mask *Mask, int16 Increment, int16 StopAt) {
    if (Increment > 0) {
        int16 i = Mask->NumberOfPoints - 1;
        while (i >= StopAt) {
            mask_point *CurrentPoint = &Mask->Point[i];
            mask_point *NextPoint = &Mask->Point[i + Increment];
            *NextPoint = *CurrentPoint;
            i--;
        }
    } else  {
        int16 i = StopAt;
        while (i <= Mask->NumberOfPoints - 1) {
            mask_point *CurrentPoint = &Mask->Point[i];
            mask_point *NextPoint = &Mask->Point[i - Increment];
            *CurrentPoint = *NextPoint;
            i++;
        }
    }
}

static void
Mask_DeletePoint(memory *Memory, mask *Mask, uint16 Index)
{
    History_Entry_Commit(Memory, action_entry_default, "Delete keyframe");
    mask_point *MaskPointIndex = &Mask->Point[Index];
    History_Action_StoreData(Memory, MaskPointIndex, sizeof(mask_point));

    History_Action_Change_Decrement(Memory, &Mask->NumberOfPoints, action_type_change_u16);
    // History_Action_Shift(Memory, action_type_shift_bezier, Mask, -1, Index);
    void *StartingAddress = &Mask->Point[0];
    History_Action_Shift_2(Memory, StartingAddress, sizeof(mask_point), Mask->NumberOfPoints, -1, Index);
    // Mask_ShiftPointers(Mask, -1, Index);
    History_Entry_End(Memory);
}

// It's more useful to input the ratio here instead of the cursor position
// since we have to use it to calculate the four new handle lengths (two on the
// new point and one on each edge).
static void
Mask_AddPointToCurve(memory *Memory, mask *Mask, uint16 Index, real32 ratio)
{
    mask_point *Point0 = &Mask->Point[Index];
    mask_point *Point1 = &Mask->Point[Index+1];
    if (Index + 1 == Mask->NumberOfPoints)
        Point1 = &Mask->Point[0];

    v2 Point0_Pos_Right = Point0->Pos + Point0->TangentRight;
    v2 Point1_Pos_Left = Point1->Pos + Point1->TangentLeft;
    v2 Handle0_Half   = Line_RatioToPoint(Point0->Pos,      Point0_Pos_Right, ratio);
    v2 Handle1_Half   = Line_RatioToPoint(Point1_Pos_Left,  Point1->Pos,      ratio);
    v2 Top_Half       = Line_RatioToPoint(Point0_Pos_Right, Point1_Pos_Left,  ratio);
    v2 NewHandleLeft  = Line_RatioToPoint(Handle0_Half,     Top_Half,         ratio);
    v2 NewHandleRight = Line_RatioToPoint(Top_Half,         Handle1_Half,     ratio);
    v2 NewPos         = Line_RatioToPoint(NewHandleLeft,    NewHandleRight,   ratio);

    History_Entry_Commit(Memory, action_entry_default, "Add point to curve");

    v2 NewPoint0Pos = -(Point0->Pos - Handle0_Half);
    v2 NewPoint1Pos = -(Point1->Pos - Handle1_Half);
    History_Action_Change_V2(Memory, &Point0->TangentRight, &Point0->TangentRight, &NewPoint0Pos);
    History_Action_Change_V2(Memory, &Point1->TangentLeft, &Point1->TangentLeft, &NewPoint1Pos);

    void *StartingAddress = &Mask->Point[0];
    History_Action_Shift_2(Memory, StartingAddress, sizeof(mask_point), Mask->NumberOfPoints, 1, Index);

    mask_point *PointToAdd = &Mask->Point[Index+1];

    // NOTE(fox): The above shift duplicates the keyframe at Index into where
    // we're writing, Index+1. I'm using the Change action (which is normally
    // for changing values that already exist) on this intermediate keyframe
    // slot to save having to write a bunch of special actions for shifting and
    // adding new data.

    History_Action_Change_V2(Memory, &PointToAdd->Pos, &PointToAdd->Pos, &NewPos);
    v2 NewLeftPos = -(NewPos - NewHandleLeft);
    v2 NewRightPos = -(NewPos - NewHandleRight);
    History_Action_Change_V2(Memory, &PointToAdd->TangentLeft, &PointToAdd->TangentLeft, &NewLeftPos);
    History_Action_Change_V2(Memory, &PointToAdd->TangentRight, &PointToAdd->TangentRight, &NewRightPos);

    History_Action_Change_Increment(Memory, &Mask->NumberOfPoints, action_type_change_u16);
    History_Entry_End(Memory);
}

static void
Mask_RasterizePoints(mask *Mask)
{
    Mask->NumberOfVerts = 0;
    for (int i = 0; i < Mask->NumberOfPoints; i++) {
        mask_point Point0 = Mask->Point[i];
        mask_point Point1 = Mask->Point[i+1];
        if (i+1 == Mask->NumberOfPoints)
            Point1 = Mask->Point[0];

        if (Point0.HandleBezier && Point1.HandleBezier) {
            Bezier_CubicCalcPoints(Point0.Pos, Point0.Pos + Point0.TangentRight, Point1.Pos + Point1.TangentLeft, Point1.Pos,
                                   Mask->TriangulatedPointCache, &Mask->NumberOfVerts);
        } else if (Point0.HandleBezier) {
            Bezier_CubicCalcPoints(Point0.Pos, Point0.Pos + Point0.TangentRight, Point1.Pos, Point1.Pos,
                                   Mask->TriangulatedPointCache, &Mask->NumberOfVerts);
        } else if (Point1.HandleBezier) {
            Bezier_CubicCalcPoints(Point0.Pos, Point0.Pos, Point1.Pos + Point1.TangentLeft, Point1.Pos,
                                   Mask->TriangulatedPointCache, &Mask->NumberOfVerts);
        } else {
            real32 *Data = (real32 *)Mask->TriangulatedPointCache + Mask->NumberOfVerts*3;
            *(Data++) = Point0.Pos.x;
            *(Data++) = Point0.Pos.y;
            *(Data++) = 0;
            // NOTE(fox): CubicCalcPoints sometimes misses generating the start
            // point of the next path in the above two cases, so I'm making
            // straight lines always add both points as a hotfix. This leads
            // to cases of duplicate verts, but it doesn't seem like it harms
            // the rendering in any way.
            *(Data++) = Point1.Pos.x;
            *(Data++) = Point1.Pos.y;
            *(Data++) = 0;
            Mask->NumberOfVerts += 2;
        }
    }
}

void Mask_TriangulateAndRasterize(memory *Memory, project_layer *Layer, mask *Mask)
{
    if (!Mask->TriangulatedPointCache) {
        Mask->TriangulatedPointCache = AllocateMemory(Memory, 50*1024, P_VectorPoints);
    }
    Mask_RasterizePoints(Mask);

    GL_RasterizeShape(Layer, Mask);
}
#endif