closes #38 - only vital panic calls are remained

canvas.go

@@ -1,7 +1,6 @@
 package clui
 
 import (
-	"fmt"
 	xs "github.com/huandu/xstrings"
 	term "github.com/nsf/termbox-go"
 )
@@ -18,8 +17,11 @@ type FrameBuffer struct {
 
 // NewFrameBuffer creates new buffer. Width and height of a new buffer cannot be less than 3
 func NewFrameBuffer(w, h int) *FrameBuffer {
-	if w < 3 || h < 3 {
+	if w < 3 {
-		panic(fmt.Sprintf("Invalid size: %vx%v.", w, h))
+		w = 3
+	}
+	if h < 3 {
+		h = 3
 	}
 
 	c := new(FrameBuffer)
@@ -39,12 +41,15 @@ FrameBuffer is recreated and cleared with default colors. Both FrameBuffer width
 height must be greater than 2
 */
 func (fb *FrameBuffer) SetSize(w, h int) {
-	if w == fb.w && h == fb.h {
+	if w < 3 {
-		return
+		w = 3
+	}
+	if h < 3 {
+		h = 3
 	}
 
-	if w < 3 || h < 3 {
+	if w == fb.w && h == fb.h {
-		panic(fmt.Sprintf("Invalid size: %vx%v.", w, h))
+		return
 	}
 
 	fb.w, fb.h = w, h
@@ -223,15 +228,11 @@ func (fb *FrameBuffer) DrawFrame(x, y, w, h int, fg, bg term.Attribute, frameCha
 		return
 	}
 
-	if frameChars == "" {
+	if xs.Len(frameChars) < 6 {
 		frameChars = "─│┌┐└┘"
 	}
 
 	parts := []rune(frameChars)
-	if len(parts) < 6 {
-		panic("Invalid theme: single border")
-	}
-
 	H, V, UL, UR, DL, DR := parts[0], parts[1], parts[2], parts[3], parts[4], parts[5]
 
 	if h == 1 {

composer.go

@@ -36,11 +36,12 @@ func (c *Composer) initBuffer() {
 	c.canvas.Clear(ColorBlack)
 }
 
-// InitLibrary initializes library and starts console management
+// InitLibrary initializes library and starts console management.
+// Retuns nil in case of error
 func InitLibrary() *Composer {
 	err := term.Init()
 	if err != nil {
-		panic(err)
+		return nil
 	}
 
 	c := new(Composer)
@@ -128,13 +129,13 @@ func (c *Composer) checkWindowUnderMouse(screenX, screenY int) (View, HitResult)
 	return nil, HitOutside
 }
 
-func (c *Composer) activateView(view View) {
+func (c *Composer) activateView(view View) bool {
 	if c.topView() == view {
 		for _, v := range c.views {
 			v.SetActive(false)
 		}
 		view.SetActive(true)
-		return
+		return true
 	}
 
 	var wList []View
@@ -150,11 +151,12 @@ func (c *Composer) activateView(view View) {
 	}
 
 	if !found {
-		panic("Invalid view to activate")
+		return false
 	}
 
 	view.SetActive(true)
 	c.views = append(wList, view)
+	return true
 }
 
 func (c *Composer) moveActiveWindowToBottom() bool {
@@ -176,7 +178,9 @@ func (c *Composer) moveActiveWindowToBottom() bool {
 	}
 
 	c.views[0] = last
-	c.activateView(c.topView())
+	if !c.activateView(c.topView()) {
+		return false
+	}
 
 	event = Event{Type: EventActivate, X: 1} // send 'activated'
 	c.sendEventToActiveView(event)

control_base.go

@@ -1,7 +1,6 @@
 package clui
 
 import (
-	"fmt"
 	term "github.com/nsf/termbox-go"
 	"log"
 )
@@ -46,13 +45,22 @@ func (c *ControlBase) Size() (int, int) {
 // SetSize changes control size. Constant DoNotChange can be
 // used as placeholder to indicate that the control attrubute
 // should be unchanged.
-// Method panics if new size is less than minimal size
 func (c *ControlBase) SetSize(width, height int) {
-	if width != DoNotChange && (width > 1000 || width < c.minW) {
+	if width != DoNotChange {
-		panic(fmt.Sprintf("Invalid width: %v", width))
+		if width > 1000 {
+			width = 1000
+		}
+		if width < c.minW {
+			width = c.minW
+		}
+	}
+	if height != DoNotChange {
+		if height > 200 {
+			height = 200
+		}
+		if height < c.minH {
+			height = c.minH
 		}
-	if height != DoNotChange && (height > 200 || height < c.minH) {
-		panic(fmt.Sprintf("Invalid height: %v", height))
 	}
 
 	if width != DoNotChange {

dialog.go

@@ -151,11 +151,13 @@ func (d *ConfirmationDialog) Result() int {
 // selectedItem is the index of the item that is selected after
 //  the dialog is created
 // typ is a selection type: ListBox or RadioGroup
+// Returns nil in case of creation process fails, e.g, if item list is empty
 func NewSelectDialog(c *Composer, title string, items []string, selectedItem int, typ SelectDialogType) *SelectDialog {
 	dlg := new(SelectDialog)
 
 	if len(items) == 0 {
-		panic("Item list must contain at least 1 item")
+		// Item list must contain at least 1 item
+		return nil
 	}
 
 	cw, ch := term.Size()

frame.go

@@ -119,7 +119,8 @@ func (f *Frame) RecalculateConstraints() {
 // its minimal size
 func (f *Frame) AddChild(c Control, scale int) {
 	if f.view.ChildExists(c) {
-		panic("Frame: Cannot add the same control twice")
+		// Frame: Cannot add the same control twice
+		return
 	}
 
 	c.SetScale(scale)
@@ -135,10 +136,11 @@ func (f *Frame) Children() []Control {
 
 // SetPack changes the direction of children packing.
 // Changing pack type on the fly is not always possible:
-// it panics if a frame already contains children
+// it does nothing if a frame already contains children
 func (f *Frame) SetPack(pk PackType) {
 	if len(f.children) > 0 {
-		panic("Control already has children")
+		// Control already has children
+		return
 	}
 
 	f.pack = pk

interface.go

@@ -104,7 +104,6 @@ type View interface {
 	// SetSize changes control size. Constant DoNotChange can be
 	// used as placeholder to indicate that the control attrubute
 	// should be unchanged.
-	// Method panics if new size is less than minimal size
 	SetSize(int, int)
 	// Pos returns the current control position: X and Y.
 	// For View the position's origin is top left corner of console window,
@@ -173,7 +172,7 @@ type View interface {
 	SetPaddings(int, int, int, int)
 	// AddChild add control to a list of view children. Minimal size
 	// of the view calculated as a sum of sizes of its children.
-	// Method panics if the same control is added twice
+	// Method does nothing if the control is already added
 	AddChild(Control, int)
 	// SetPack changes the direction of children packing
 	SetPack(PackType)
@@ -251,7 +250,6 @@ type Control interface {
 	// SetSize changes control size. Constant DoNotChange can be
 	// used as placeholder to indicate that the control attrubute
 	// should be unchanged.
-	// Method panics if new size is less than minimal size
 	SetSize(int, int)
 	// Scale return scale coefficient that is used to calculate
 	// new control size after its parent resizes.

theme.go

@@ -40,8 +40,8 @@ Theme file is a simple text file that has similar to INI file format:
 6. Non-system keys are divided into two groups: Colors and Objects
     Colors are the keys that end with 'Back' or 'Text' - background
         and text color, respectively. If theme manager cannot
-        value to color it panics. See Color*Back * Color*Text constants,
+        value to color it uses black color. See Color*Back * Color*Text
-        just drop 'Color' at the beginning of key name.
+        constants, just drop 'Color' at the beginning of key name.
         Rules of converting text to color:
         1. If the value does not end neither with 'Back' nor with 'Text'
             it is considered as raw attribute value(e.g, 'green bold')
@@ -60,9 +60,10 @@ Theme file is a simple text file that has similar to INI file format:
             Better way is:
                 Viewback=parent.ViewText
                 ViewText=parent.ViewBack
-        Converting text to real color panics if a) the string does not look
+        Converting text to real color fails and retuns black color if
-            like real color(e.g, typo as in 'grean bold'), b) parent theme
+            a) the string does not look like real color(e.g, typo as in
-            has not loaded yet, c) parent theme does not have the color
+            'grean bold'), b) parent theme has not loaded yet, c) parent
+            theme does not have the color
             with the same name
     Other keys are considered as objects - see Obj* constants, just drop
         'Obj' at the beginning of the key name
@@ -180,7 +181,9 @@ func (s *ThemeManager) Reset() {
 	s.themes[defaultTheme] = defTheme
 }
 
-// SysColor returns attribute by its id for the current theme
+// SysColor returns attribute by its id for the current theme.
+// The method panics if theme loop is detected - check if
+// parent attribute is correct
 func (s *ThemeManager) SysColor(color string) term.Attribute {
 	sch, ok := s.themes[s.current]
 	if !ok {
@@ -216,7 +219,9 @@ func (s *ThemeManager) SysColor(color string) term.Attribute {
 }
 
 // SysObject returns object look by its id for the current
-// theme. E.g, border lines for frame or arrows for scrollbar
+// theme. E.g, border lines for frame or arrows for scrollbar.
+// The method panics if theme loop is detected - check if
+// parent attribute is correct
 func (s *ThemeManager) SysObject(object string) string {
 	sch, ok := s.themes[s.current]
 	if !ok {

window.go

@@ -1,7 +1,6 @@
 package clui
 
 import (
-	"fmt"
 	term "github.com/nsf/termbox-go"
 	"log"
 )
@@ -62,18 +61,27 @@ func NewWindow(parent Screen, x, y, w, h int, title string) *Window {
 // SetSize changes control size. Constant DoNotChange can be
 // used as placeholder to indicate that the control attrubute
 // should be unchanged.
-// Method panics if new size is less than minimal size.
 // View automatically recalculates position and size of its children after changing its size
 func (w *Window) SetSize(width, height int) {
 	if width == w.width && height == w.height {
 		return
 	}
 
-	if width != DoNotChange && (width > 1000 || width < w.minW) {
+	if width != DoNotChange {
-		panic(fmt.Sprintf("Invalid width: %v", width))
+		if width > 1000 {
+			width = 1000
+		}
+		if width < w.minW {
+			width = w.minW
+		}
+	}
+	if height != DoNotChange {
+		if height > 200 {
+			height = 200
+		}
+		if height < w.minH {
+			height = w.minH
 		}
-	if height != DoNotChange && (height > 200 || height < w.minH) {
-		panic(fmt.Sprintf("Invalid height: %v", height))
 	}
 
 	if width != DoNotChange {
@@ -120,16 +128,14 @@ func (w *Window) SetConstraints(width, height int) {
 }
 
 // Draw paints the view screen buffer to a canvas. It does not
-// repaint all view children
+// repaint all view children.
+// Method does nothing if coordinates are outside canvas
 func (w *Window) Draw(canvas Canvas) {
 	for y := 0; y < w.height; y++ {
 		for x := 0; x < w.width; x++ {
 			s, ok := w.canvas.Symbol(x, y)
 			if ok {
 				canvas.PutSymbol(x+w.x, y+w.y, s)
-			} else {
-				wx, wy := w.Size()
-				panic(fmt.Sprintf("Invalid x, y: %vx%v of %vx%v", x, y, wx, wy))
 			}
 		}
 	}
@@ -242,11 +248,12 @@ func (w *Window) Buttons() ViewButton {
 	return w.buttons
 }
 
-// SetPack changes the direction of children packing. Call the method only before any child is added to view. Otherwise, the method
+// SetPack changes the direction of children packing. Call the method
-// panics if a view already contains children
+// only before any child is added to view. Otherwise, the method
+// does nothing
 func (w *Window) SetPack(pk PackType) {
 	if len(w.children) > 0 {
-		panic("Control already has children")
+		return
 	}
 
 	w.pack = pk
@@ -289,10 +296,10 @@ func (w *Window) RegisterControl(c Control) {
 
 // AddChild add control to a list of view children. Minimal size
 // of the view calculated as a sum of sizes of its children.
-// Method panics if the same control is added twice
+// Method does nothing if the control is already added
 func (w *Window) AddChild(c Control, scale int) {
 	if w.ChildExists(c) {
-		panic("Cannot add the same control twice")
+		return
 	}
 
 	c.SetScale(scale)