A simple widget to display the termshark log file

This uses gowid's terminal widget. Termshark's main.pager setting is
used to open the log file, if configured; if not, the environment
variable PAGER is tried.

This is intended to help diagnose errors that are not displayed with
enough information in the UI.

widgets/logviewer/logviewer.go

@@ -0,0 +1,84 @@
+// Copyright 2019-2020 Graham Clark. All rights reserved.  Use of this source
+// code is governed by the MIT license that can be found in the LICENSE
+// file.
+
+// +build !windows
+
+// Package logviewer provides a widget to view termshark's log file in a terminal
+// via a pager program.
+package logviewer
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/gcla/gowid"
+	"github.com/gcla/gowid/widgets/hpadding"
+	"github.com/gcla/gowid/widgets/null"
+	"github.com/gcla/gowid/widgets/pile"
+	"github.com/gcla/gowid/widgets/terminal"
+	"github.com/gcla/gowid/widgets/text"
+	"github.com/gcla/termshark/v2"
+)
+
+//======================================================================
+
+type Widget struct {
+	gowid.IWidget
+}
+
+// New - a bit clumsy, UI will always be legit, but error represents terminal failure
+func New(cb gowid.IWidgetChangedCallback) (*Widget, error) {
+	logfile := termshark.CacheFile("termshark.log")
+
+	var args []string
+	pager := termshark.ConfString("main.pager", "")
+	if pager == "" {
+		pager = os.Getenv("PAGER")
+	}
+	if pager == "" {
+		args = []string{"less", "+G", logfile}
+	} else {
+		args = []string{"sh", "-c", fmt.Sprintf("%s %s", pager, logfile)}
+	}
+
+	var term gowid.IWidget
+	var termC *terminal.Widget
+	var errTerm error
+	termC, errTerm = terminal.New(args)
+	if errTerm != nil {
+		term = null.New()
+	} else {
+		termC.OnProcessExited(cb)
+		term = termC
+	}
+
+	header := hpadding.New(
+		text.New(fmt.Sprintf("Logs - %s", logfile)),
+		gowid.HAlignMiddle{},
+		gowid.RenderFixed{},
+	)
+
+	main := pile.New([]gowid.IContainerWidget{
+		&gowid.ContainerWidget{
+			IWidget: header,
+			D:       gowid.RenderWithUnits{U: 2},
+		},
+		&gowid.ContainerWidget{
+			IWidget: term,
+			D:       gowid.RenderWithWeight{W: 1.0},
+		},
+	})
+
+	res := &Widget{
+		IWidget: main,
+	}
+
+	return res, errTerm
+}
+
+//======================================================================
+// Local Variables:
+// mode: Go
+// fill-column: 110
+// End: