Modernize gfx

[peterhellberg]

Modernization pass though the gfx package, extracted HTTP related code into its own package (gfxhttp).

Will hopefully address what is asked for in #5

Important

⚠️ NO STABILITY GUARANTEES ⚠️

This package is just something I've made for fun.

Breaking API changes (require code edits at call sites)

Removed from root gfx — moved to new gfxhttp subpackage:

• gfx.HTTP (type)
• gfx.HTTPClient (var)
• gfx.Get, gfx.GetPNG, gfx.GetImage, gfx.GetTileset
• gfx.GeoTileServer (type)
• gfx.GTS (constructor)
• gfx.GeoTileServer.{GetImage, DrawTile, DrawNeighbors, DrawTileAndNeighbors}
• gfx.GeoTile.GetImage (method on still-present GeoTile)

Replacement: import "github.com/peterhellberg/gfx/gfxhttp"

Renamed:

• gfx.DrawCicleFast → gfx.DrawCircleFast (typo fix; no alias kept)

Signature changes:

• gfx.SortSlice(slice any, less func(i, j int) bool) →
  gfx.SortSlice[S ~[]E, E any](s S, cmp func(a, b E) int).
  • Comparator switched from index-based bool to element-pair cmp.Compare-style int
    (matches slices.SortFunc).
• gfx.Sign, gfx.Clamp, gfx.Lerp are now generic on new gfx.Numeric /
  gfx.Signed constraints (or cmp.Ordered for Clamp).
  Float64 callers keep working via type inference.
  • Watch-out: gfx.Lerp(0, 2, 0.1) (untyped int literals) now infers T = int
    and returns 0. Pass float literals or gfx.Lerp[float64](...).
  • Anyone who captured one of these as a function value (f := gfx.Sign) now needs to
    instantiate (f := gfx.Sign[float64]).

Module floor:

• go.mod raised from go 1.17 to go 1.25. Consumers must use Go 1.25 or newer.

Changes

• go: Bump versions to current supported versions 1.25.x and 1.26.x
• rand: Replaced the deprecated rand.Seed call with a package-level *rand.Rand
• palette: Palette.Random now calls gfx.RandIntn instead of rand.Intn
• draw: Replaced the m.X != w / m.Y != h termination with r.Min.X < r.Max.X / r.Min.Y < r.Max.Y in both DrawPalettedImage and DrawPalettedLayer
• draw: Renamed DrawCicleFast → DrawCircleFast
• gfx: Replace interface{} with any
• draw_int: Removed bare return statements in DrawIntRectangle and DrawIntFilledRectangle
• image: Replaced the per-pixel DrawColorOver path with an inline premultiplied-alpha blend
• gfx: Moved HTTP related code into new gfxhttp package
• gfxhttp: Thread context.Context through all requests
• math: Make Sign, Clamp, and Lerp generic via new Numeric, Signed, and cmp.Ordered constraints
• sort: Replace SortSlice reflection wrapper with generic slices.SortFunc-backed implementation
• license: Update copyright year
• doc: Update copyright year
• examples: Update examples
• block: Color every vertex in Block.Triangles so faces render uniformly instead of partially black
• triangle: Round Triangle.Bounds Max up so adjacent triangles meet without gaps and right/bottom edge pixels aren't skipped
• paletted: Honor Rect.Min in Paletted.PixOffset so non-origin Paletted images index Pix correctly
• gfx: Drop legacy // +build directives now that go.mod is on Go 1.25
• examples: Use gfx.V and keyed SignedDistance literals to satisfy go vet, and re-embed README snippets
• gfx: Modernize counted for loops to range-over-int (go fix)
• examples/gfx-example-animation: Slice 5 palette colors so the flower stem renders instead of falling back to the background
• draw: Use the triangle's first vertex color in DrawTrianglesWireframe instead of looking up the color at world origin
• paletted: Bounds-check ColorIndexAt and SetColorIndex so out-of-range coordinates return 0 / no-op instead of panicking
• block: Round Block.DrawBounds Max up so fractional Rect edges don't lose a column or row to int() truncation
• gfxhttp: Add tests for raw Get response, GetImage decode path, WithHTTPClient(nil) no-op, and TileServer.DrawTile
• doc: List WithHeader alongside the other gfxhttp options
• gfx: Drop !tinygo build constraints from files whose imports TinyGo now supports (hopefully)