gfx/drivers: drop dead prim_to_d3d helpers in d3d8/d3d9_cg/d3d9_hlsl

Each of the three D3D fixed-pipeline drivers carries an identical
gfx_display_prim_to_d3d{8,9_cg,9_hlsl}_enum helper plus a caller-
side switch on draw->prim_type.  Both are dead.

Every gfx_display_ctx_draw_t in the codebase sets prim_type to
GFX_DISPLAY_PRIM_TRIANGLESTRIP before invoking dispctx->draw.  All
19 "prim_type =" assignments under gfx/, menu/, and gfx/widgets/
assign TRIANGLESTRIP -- never TRIANGLES, never NONE.  Every local
declaration of the draw struct assigns prim_type before the draw
call (swept each one).  At runtime the helper switch always hits
the TRIANGLESTRIP arm and the caller's per-call branch always
takes the tristrip path.

The dead non-tristrip branch was also buggy: it mapped TRIANGLES
to D3DPT_TRIANGLESTRIP (wrong primitive -- gl1/2/3 correctly map
it to GL_TRIANGLES) and used count = vertices (wrong formula for
DrawPrimitive, which takes PrimitiveCount; the right formula is
vertices/3).  And the helpers' TODO/FIXME default returned zero,
which is not a legal D3DPRIMITIVETYPE value (the enum starts at
D3DPT_POINTLIST = 1) -- a debug runtime would reject the call.

Inline D3DPT_TRIANGLESTRIP at the DrawPrimitive site, drop the
helpers and the dead caller branches, drop the now-unused
D3DPRIMITIVETYPE locals.  Document at each call site that this
assumes TRIANGLESTRIP and would need to grow back into a switch
if a future non-tristrip caller appears.

While here, harden d3d9_cg and d3d9_hlsl against vertices < 3.
Both used count = vertices - 2 unconditionally, which on an
unsigned subtraction with vertices < 2 wraps to a huge primitive
count and walks off the vertex buffer in the GPU.  d3d8 already
had this guard; the d3d9 pair did not.  No caller passes < 3
vertices today, but the same "no caller does this" reasoning is
what kept the dead switch alive, so add the guard symmetrically.

Net -38 lines.  No behavioural change for any existing caller.

gfx/drivers/d3d8.c

@@ -657,23 +657,6 @@ static void *gfx_display_d3d8_get_default_mvp(void *data)
    return &id;
 }
 
-static INT32 gfx_display_prim_to_d3d8_enum(
-      enum gfx_display_prim_type prim_type)
-{
-   switch (prim_type)
-   {
-      case GFX_DISPLAY_PRIM_TRIANGLES:
-      case GFX_DISPLAY_PRIM_TRIANGLESTRIP:
-         return D3DPT_TRIANGLESTRIP;
-      case GFX_DISPLAY_PRIM_NONE:
-      default:
-         break;
-   }
-
-   /* TODO/FIXME - hack */
-   return 0;
-}
-
 static void gfx_display_d3d8_blend_begin(void *data)
 {
    d3d8_video_t *d3d             = (d3d8_video_t*)data;
@@ -710,7 +693,6 @@ static void gfx_display_d3d8_draw(gfx_display_ctx_draw_t *draw,
    math_matrix_4x4 mop, m1, m2;
    LPDIRECT3DVERTEXBUFFER8 vbo;
    LPDIRECT3DDEVICE8 dev;
-   D3DPRIMITIVETYPE type;
    unsigned start                = 0;
    unsigned count                = 0;
    d3d8_video_t *d3d             = (d3d8_video_t*)data;
@@ -1005,32 +987,30 @@ static void gfx_display_d3d8_draw(gfx_display_ctx_draw_t *draw,
    IDirect3DDevice8_SetTextureStageState(dev, 0,
          (D3DTEXTURESTAGESTATETYPE)D3DTSS_ALPHAARG2, D3DTA_DIFFUSE);
 
-   type  = gfx_display_prim_to_d3d8_enum(draw->prim_type);
    start = d3d->menu_display.offset;
 
-   /* For tristrips, the primitive count is vertices - 2. Guard
-    * against vertices < 3 which would underflow the unsigned
+   /* Every caller in the codebase sets draw->prim_type to
+    * GFX_DISPLAY_PRIM_TRIANGLESTRIP, and the draw->coords vertices
+    * are laid out as a strip.  Hard-code D3DPT_TRIANGLESTRIP and the
+    * (vertices - 2) primitive-count formula here.  If a future
+    * caller passes TRIANGLES or another primitive type, this site
+    * will need to grow back into a switch -- but with no current
+    * non-tristrip caller, the dead branch was just buggy: it mapped
+    * TRIANGLES to D3DPT_TRIANGLESTRIP (the wrong type) and used
+    * count = vertices (the wrong count formula for D3D, which
+    * expects PrimitiveCount, not vertex count).
+    *
+    * Guard against vertices < 3 which would underflow the unsigned
     * subtraction and pass a huge primitive count to the GPU. */
-   if (draw->prim_type == GFX_DISPLAY_PRIM_TRIANGLESTRIP)
-   {
-      if (draw->coords->vertices < 3)
-      {
-         d3d->menu_display.offset += draw->coords->vertices;
-         return;
-      }
-      count = draw->coords->vertices - 2;
-   }
-   else
-      count = draw->coords->vertices;
-
-   if (count == 0)
+   if (draw->coords->vertices < 3)
    {
       d3d->menu_display.offset += draw->coords->vertices;
       return;
    }
+   count = draw->coords->vertices - 2;
 
    IDirect3DDevice8_BeginScene(dev);
-   IDirect3DDevice8_DrawPrimitive(dev, type, start, count);
+   IDirect3DDevice8_DrawPrimitive(dev, D3DPT_TRIANGLESTRIP, start, count);
    IDirect3DDevice8_EndScene(dev);
 
    d3d->menu_display.offset += draw->coords->vertices;

gfx/drivers/d3d9cg.c

@@ -476,23 +476,6 @@ static const float d3d9_cg_tex_coords[8] = {
    1, 0
 };
 
-static INT32 gfx_display_prim_to_d3d9_cg_enum(
-      enum gfx_display_prim_type prim_type)
-{
-   switch (prim_type)
-   {
-      case GFX_DISPLAY_PRIM_TRIANGLES:
-      case GFX_DISPLAY_PRIM_TRIANGLESTRIP:
-         return D3DPT_TRIANGLESTRIP;
-      case GFX_DISPLAY_PRIM_NONE:
-      default:
-         break;
-   }
-
-   /* TODO/FIXME - hack */
-   return 0;
-}
-
 static void gfx_display_d3d9_cg_blend_begin(void *data)
 {
    d3d9_video_t *d3d = (d3d9_video_t*)data;
@@ -672,7 +655,6 @@ static void gfx_display_d3d9_cg_draw(gfx_display_ctx_draw_t *draw,
 {
    unsigned i;
    LPDIRECT3DDEVICE9 dev;
-   D3DPRIMITIVETYPE type;
    bool has_vertex_data;
    unsigned start                = 0;
    unsigned count                = 0;
@@ -1038,13 +1020,22 @@ static void gfx_display_d3d9_cg_draw(gfx_display_ctx_draw_t *draw,
 
    gfx_display_d3d9_cg_bind_texture(draw, d3d);
 
-   type  = (D3DPRIMITIVETYPE)gfx_display_prim_to_d3d9_cg_enum(draw->prim_type);
    start = d3d->menu_display.offset;
-   count = draw->coords->vertices -
-         ((draw->prim_type == GFX_DISPLAY_PRIM_TRIANGLESTRIP)
-          ? 2 : 0);
 
-   IDirect3DDevice9_DrawPrimitive(dev, type, start, count);
+   /* Every caller in the codebase sets draw->prim_type to
+    * GFX_DISPLAY_PRIM_TRIANGLESTRIP, so the per-call switch on the
+    * primitive type that used to live here was dead.  See the
+    * matching comment in d3d8.c's gfx_display_d3d8_draw for why we
+    * also harden against vertices < 3 (the tristrip count formula
+    * vertices - 2 underflows the unsigned subtraction otherwise). */
+   if (draw->coords->vertices < 3)
+   {
+      d3d->menu_display.offset += draw->coords->vertices;
+      return;
+   }
+   count = draw->coords->vertices - 2;
+
+   IDirect3DDevice9_DrawPrimitive(dev, D3DPT_TRIANGLESTRIP, start, count);
 
    d3d->menu_display.offset += draw->coords->vertices;
 }

gfx/drivers/d3d9hlsl.c

@@ -709,23 +709,6 @@ static const float d3d9_hlsl_tex_coords[8] = {
 
 static LPDIRECT3DTEXTURE9 d3d9_hlsl_white_texture = NULL;
 
-static INT32 gfx_display_prim_to_d3d9_hlsl_enum(
-      enum gfx_display_prim_type prim_type)
-{
-   switch (prim_type)
-   {
-      case GFX_DISPLAY_PRIM_TRIANGLES:
-      case GFX_DISPLAY_PRIM_TRIANGLESTRIP:
-         return D3DPT_TRIANGLESTRIP;
-      case GFX_DISPLAY_PRIM_NONE:
-      default:
-         break;
-   }
-
-   /* TODO/FIXME - hack */
-   return 0;
-}
-
 static void gfx_display_d3d9_hlsl_blend_begin(void *data)
 {
    d3d9_video_t *d3d = (d3d9_video_t*)data;
@@ -777,7 +760,6 @@ static void gfx_display_d3d9_hlsl_draw(gfx_display_ctx_draw_t *draw,
 {
    unsigned i;
    LPDIRECT3DDEVICE9 dev;
-   D3DPRIMITIVETYPE type;
    bool has_vertex_data;
    unsigned start                = 0;
    unsigned count                = 0;
@@ -1099,13 +1081,22 @@ static void gfx_display_d3d9_hlsl_draw(gfx_display_ctx_draw_t *draw,
    if (draw && draw->texture)
       gfx_display_d3d9_bind_texture(draw, d3d);
 
-   type  = (D3DPRIMITIVETYPE)gfx_display_prim_to_d3d9_hlsl_enum(draw->prim_type);
    start = d3d->menu_display.offset;
-   count = draw->coords->vertices -
-         ((draw->prim_type == GFX_DISPLAY_PRIM_TRIANGLESTRIP)
-          ? 2 : 0);
 
-   IDirect3DDevice9_DrawPrimitive(dev, type, start, count);
+   /* Every caller in the codebase sets draw->prim_type to
+    * GFX_DISPLAY_PRIM_TRIANGLESTRIP, so the per-call switch on the
+    * primitive type that used to live here was dead.  See the
+    * matching comment in d3d8.c's gfx_display_d3d8_draw for why we
+    * also harden against vertices < 3 (the tristrip count formula
+    * vertices - 2 underflows the unsigned subtraction otherwise). */
+   if (draw->coords->vertices < 3)
+   {
+      d3d->menu_display.offset += draw->coords->vertices;
+      return;
+   }
+   count = draw->coords->vertices - 2;
+
+   IDirect3DDevice9_DrawPrimitive(dev, D3DPT_TRIANGLESTRIP, start, count);
 
    d3d->menu_display.offset += draw->coords->vertices;
 }