Crosshair Option + Doodad Editor crash fix

* The level scroll logic was getting a null pointer crash if you open a
  doodad rather than a level file.
* Add a crosshair option to the level editor, configurable in the Game
  Settings window.

cmd/doodle/main.go

@@ -20,6 +20,7 @@ import (
 	"git.kirsle.net/apps/doodle/pkg/shmem"
 	"git.kirsle.net/apps/doodle/pkg/sound"
 	"git.kirsle.net/apps/doodle/pkg/usercfg"
+	"git.kirsle.net/go/render"
 	"git.kirsle.net/go/render/sdl"
 	"github.com/urfave/cli/v2"
 
@@ -62,6 +63,11 @@ func main() {
 		log.Error("Error loading user settings (defaults will be used): %s", err)
 	}
 
+	// Set default user settings.
+	if usercfg.Current.CrosshairColor == render.Invisible {
+		usercfg.Current.CrosshairColor = balance.DefaultCrosshairColor
+	}
+
 	app.Version = fmt.Sprintf("%s build %s%s. Built on %s",
 		branding.Version,
 		Build,

pkg/balance/theme.go

@@ -187,6 +187,8 @@ var (
 	ButtonBabyBlue = style.DefaultButton
 	ButtonPink     = style.DefaultButton
 	ButtonLightRed = style.DefaultButton
+
+	DefaultCrosshairColor = render.RGBA(0, 153, 255, 255)
 )
 
 // Customize the various button styles.

pkg/doodle.go

@@ -69,6 +69,7 @@ func New(debug bool, engine render.Engine) *Doodle {
 	// Make the render engine globally available. TODO: for wasm/ToBitmap
 	shmem.CurrentRenderEngine = engine
 	shmem.Flash = d.Flash
+	shmem.FlashError = d.FlashError
 	shmem.Prompt = d.Prompt
 
 	if debug {
@@ -240,6 +241,8 @@ func (d *Doodle) MakeSettingsWindow(supervisor *ui.Supervisor) *ui.Window {
 		DebugCollision:     &DebugCollision,
 		HorizontalToolbars: &usercfg.Current.HorizontalToolbars,
 		EnableFeatures:     &usercfg.Current.EnableFeatures,
+		CrosshairSize:      &usercfg.Current.CrosshairSize,
+		CrosshairColor:     &usercfg.Current.CrosshairColor,
 	}
 	return windows.MakeSettingsWindow(d.width, d.height, cfg)
 }

pkg/editor_ui.go

@@ -351,6 +351,9 @@ func (u *EditorUI) Present(e render.Engine) {
 
 	u.screen.Present(e, render.Origin)
 
+	// Draw the crosshair over the level canvas, but not over UI popups.
+	uix.DrawCrosshair(e, u.Canvas, usercfg.Current.CrosshairColor, usercfg.Current.CrosshairSize)
+
 	// Draw any windows being managed by Supervisor.
 	u.Supervisor.Present(e)
 

pkg/shmem/globals.go

@@ -24,6 +24,7 @@ var (
 
 	// Globally available Flash() function so we can emit text to the Doodle UI.
 	Flash      func(string, ...interface{})
+	FlashError func(string, ...interface{})
 
 	// Globally available Prompt() function.
 	Prompt func(string, func(string))

pkg/uix/canvas_scrolling.go

@@ -116,6 +116,11 @@ func (w *Canvas) loopConstrainScroll() error {
 		return errors.New("NoLimitScroll enabled")
 	}
 
+	// Levels only.
+	if w.level == nil {
+		return nil
+	}
+
 	var (
 		capped    bool
 		maxWidth  = w.level.MaxWidth

pkg/uix/crosshair.go

@@ -0,0 +1,70 @@
+package uix
+
+import (
+	"git.kirsle.net/apps/doodle/pkg/shmem"
+	"git.kirsle.net/go/render"
+	"git.kirsle.net/go/ui"
+)
+
+/*
+Functions for the Crosshair feature of the game.
+
+NOT dependent on Canvas!
+*/
+
+type Crosshair struct {
+	LengthPct float64 // between 0 and 1
+	Widget    ui.Widget
+}
+
+func NewCrosshair(child ui.Widget, length float64) *Crosshair {
+	return &Crosshair{
+		LengthPct: length,
+		Widget:    child,
+	}
+}
+
+// DrawCrosshair renders a crosshair on the screen. It appears while the mouse cursor is
+// over the child widget and draws within the bounds of the child widget.
+//
+// The lengthPct is an integer ranged 0 to 100 to be a percentage length of the crosshair.
+// A value of zero will not draw anything and just return.
+func DrawCrosshair(e render.Engine, child ui.Widget, color render.Color, lengthPct int) {
+	// Get our window boundaries based on our widget.
+	var (
+		Position = ui.AbsolutePosition(child)
+		Size     = child.Size()
+		Cursor   = shmem.Cursor
+		VertLine = []render.Point{
+			{X: Cursor.X, Y: Position.Y},
+			{X: Cursor.X, Y: Position.Y + Size.H},
+		}
+		HozLine = []render.Point{
+			{X: Position.X, Y: Cursor.Y},
+			{X: Position.X + Size.W, Y: Cursor.Y},
+		}
+	)
+
+	if lengthPct > 100 {
+		lengthPct = 100
+	} else if lengthPct <= 0 {
+		return
+	}
+
+	// Mouse outside our box.
+	if Cursor.X < Position.X || Cursor.X > Position.X+Size.W ||
+		Cursor.Y < Position.Y || Cursor.Y > Position.Y+Size.H {
+		return
+	}
+
+	e.DrawLine(
+		color,
+		VertLine[0],
+		VertLine[1],
+	)
+	e.DrawLine(
+		color,
+		HozLine[0],
+		HozLine[1],
+	)
+}

pkg/usercfg/usercfg.go

@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"git.kirsle.net/apps/doodle/pkg/userdir"
+	"git.kirsle.net/go/render"
 )
 
 // Settings are the available game settings.
@@ -30,6 +31,8 @@ type Settings struct {
 	// Configurable settings (pkg/windows/settings.go)
 	HorizontalToolbars bool `json:",omitempty"`
 	EnableFeatures     bool `json:",omitempty"`
+	CrosshairSize      int  `json:",omitempty"`
+	CrosshairColor     render.Color
 
 	// Secret boolprops from balance/boolprops.go
 	ShowHiddenDoodads bool `json:",omitempty"`

pkg/windows/settings.go

@@ -1,11 +1,13 @@
 package windows
 
 import (
+	"strconv"
 	"strings"
 
 	"git.kirsle.net/apps/doodle/pkg/balance"
 	"git.kirsle.net/apps/doodle/pkg/log"
 	"git.kirsle.net/apps/doodle/pkg/native"
+	"git.kirsle.net/apps/doodle/pkg/shmem"
 	"git.kirsle.net/apps/doodle/pkg/usercfg"
 	"git.kirsle.net/apps/doodle/pkg/userdir"
 	"git.kirsle.net/go/render"
@@ -24,6 +26,8 @@ type Settings struct {
 	DebugCollision     *bool
 	HorizontalToolbars *bool
 	EnableFeatures     *bool
+	CrosshairSize      *int
+	CrosshairColor     *render.Color
 
 	// Configuration options.
 	SceneName string // name of scene which called this window
@@ -106,11 +110,14 @@ func (c Settings) makeOptionsTab(tabFrame *ui.TabFrame, Width, Height int) *ui.F
 		return nil
 	}
 
+	var inputBoxWidth = 120
 	rows := []struct {
 		Header       string
 		Text         string
 		Boolean      *bool
+		Integer      *int
 		TextVariable *string
+		Color        *render.Color
 		PadY         int
 		PadX         int
 		name         string // for special cases
@@ -128,6 +135,16 @@ func (c Settings) makeOptionsTab(tabFrame *ui.TabFrame, Width, Height int) *ui.F
 			PadX:    4,
 			name:    "toolbars",
 		},
+		{
+			Integer: c.CrosshairSize,
+			Text:    "Editor: Crosshair size (0 to disable):",
+			PadX:    4,
+		},
+		{
+			Color: c.CrosshairColor,
+			Text:  "Editor: Crosshair color:",
+			PadX:  4,
+		},
 		{
 			Header: "Debug Options (temporary)",
 		},
@@ -196,6 +213,14 @@ func (c Settings) makeOptionsTab(tabFrame *ui.TabFrame, Width, Height int) *ui.F
 				PadX: row.PadX,
 			})
 			continue
+		} else {
+			// Reserve indented space where the checkbox would have gone.
+			spacer := ui.NewFrame("Spacer")
+			spacer.Resize(render.NewRect(9, 9)) // TODO: ugly UI hack ;)
+			frame.Pack(spacer, ui.Pack{
+				Side: ui.W,
+				PadX: row.PadX,
+			})
 		}
 
 		// Any leftover Text gets packed to the left.
@@ -212,6 +237,94 @@ func (c Settings) makeOptionsTab(tabFrame *ui.TabFrame, Width, Height int) *ui.F
 				Side: ui.W,
 			})
 		}
+
+		// Int variables draw as a button to prompt for new value.
+		// In future: TextVariable works here too.
+		if row.Integer != nil {
+			varButton := ui.NewButton("VarButton", ui.NewLabel(ui.Label{
+				IntVariable: row.Integer,
+				Font:        ui.MenuFont,
+			}))
+			varButton.Handle(ui.Click, func(ed ui.EventData) error {
+				shmem.Prompt(row.Text+" ", func(answer string) {
+					if answer == "" {
+						return
+					}
+
+					a, err := strconv.Atoi(answer)
+					if err != nil {
+						shmem.FlashError(err.Error())
+						return
+					}
+
+					if a < 0 {
+						a = 0
+					} else if a > 100 {
+						a = 100
+					}
+
+					*row.Integer = a
+					shmem.Flash("Crosshair size set to %d%% (WIP)", a)
+
+					// call onClick to save change to disk now
+					onClick(ed)
+				})
+				return nil
+			})
+
+			varButton.Compute(c.Engine)
+			varButton.Resize(render.Rect{
+				W: inputBoxWidth,
+				H: varButton.Size().H,
+			})
+
+			c.Supervisor.Add(varButton)
+			frame.Pack(varButton, ui.Pack{
+				Side: ui.E,
+				PadX: row.PadX,
+			})
+		}
+
+		// Color picker button.
+		if row.Color != nil {
+			btn := ui.NewButton("ColorBtn", ui.NewFrame(""))
+			style := style.DefaultButton
+			style.Background = *row.Color
+			style.HoverBackground = style.Background.Lighten(20)
+			btn.SetStyle(&style)
+			btn.Handle(ui.Click, func(ed ui.EventData) error {
+				shmem.Prompt("Enter color in hexadecimal notation: ", func(answer string) {
+					if answer == "" {
+						return
+					}
+
+					color, err := render.HexColor(answer)
+					if err != nil {
+						shmem.FlashError("Invalid color value: %s", err)
+					}
+
+					*row.Color = color
+					style.Background = color
+					style.HoverBackground = style.Background.Lighten(20)
+
+					// call onClick to save change to disk now
+					onClick(ed)
+				})
+				return nil
+			})
+
+			btn.Compute(c.Engine)
+			btn.Resize(render.Rect{
+				W: inputBoxWidth,
+				H: 20, // TODO
+			})
+
+			c.Supervisor.Add(btn)
+			frame.Pack(btn, ui.Pack{
+				Side: ui.E,
+				PadX: row.PadX,
+			})
+		}
 	}
 
 	// Button toolbar.