From 2d2f965bbe1cdd09a11b94b25069cdb2b85e4f89 Mon Sep 17 00:00:00 2001
From: Snider <snider@host.uk.com>
Date: Fri, 17 Apr 2026 18:42:21 +0100
Subject: [PATCH] Harden display query failures

---
 pkg/display/api.go      | 12 +++++---
 pkg/display/api_test.go | 68 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 4 deletions(-)

diff --git a/pkg/display/api.go b/pkg/display/api.go
index f02f3cd4..ce01a907 100644
--- a/pkg/display/api.go
+++ b/pkg/display/api.go
@@ -83,6 +83,10 @@ func unexpectedResultType(method string) error {
 	return coreerr.E(method, "unexpected result type", nil)
 }
 
+func failedQuery(method, query string) error {
+	return coreerr.E(method, query+" query failed", nil)
+}
+
 func (s *Service) GetScreens() []*Screen {
 	r := s.Core().QUERY(screen.QueryAll{})
 	if !r.OK {
@@ -105,7 +109,7 @@ func (s *Service) GetScreen(id string) (*Screen, error) {
 		if err, ok := r.Value.(error); ok {
 			return nil, err
 		}
-		return nil, nil
+		return nil, failedQuery("display.GetScreen", "screen.queryByID")
 	}
 	scr, ok := r.Value.(*screen.Screen)
 	if !ok {
@@ -120,7 +124,7 @@ func (s *Service) GetPrimaryScreen() (*Screen, error) {
 		if err, ok := r.Value.(error); ok {
 			return nil, err
 		}
-		return nil, nil
+		return nil, failedQuery("display.GetPrimaryScreen", "screen.queryPrimary")
 	}
 	scr, ok := r.Value.(*screen.Screen)
 	if !ok {
@@ -135,7 +139,7 @@ func (s *Service) GetScreenAtPoint(x, y int) (*Screen, error) {
 		if err, ok := r.Value.(error); ok {
 			return nil, err
 		}
-		return nil, nil
+		return nil, failedQuery("display.GetScreenAtPoint", "screen.queryAtPoint")
 	}
 	scr, ok := r.Value.(*screen.Screen)
 	if !ok {
@@ -390,7 +394,7 @@ func (s *Service) ReadClipboardImage() ([]byte, error) {
 		if err, ok := r.Value.(error); ok {
 			return nil, err
 		}
-		return nil, nil
+		return nil, failedQuery("display.ReadClipboardImage", "clipboard.queryImage")
 	}
 	content, ok := r.Value.(clipboard.ImageContent)
 	if !ok {
diff --git a/pkg/display/api_test.go b/pkg/display/api_test.go
index 149a5e6b..37ad023e 100644
--- a/pkg/display/api_test.go
+++ b/pkg/display/api_test.go
@@ -198,6 +198,57 @@ func TestDisplayAPI_GetScreen_BadType(t *testing.T) {
 	assert.Nil(t, got)
 }
 
+func TestDisplayAPI_GetScreen_Ugly(t *testing.T) {
+	svc, c := newTestDisplayAPIService(t)
+	c.RegisterQuery(func(_ *core.Core, q core.Query) core.Result {
+		switch q.(type) {
+		case screen.QueryByID:
+			return core.Result{OK: false}
+		default:
+			return core.Result{}
+		}
+	})
+
+	got, err := svc.GetScreen("screen-1")
+
+	require.Error(t, err)
+	assert.Nil(t, got)
+}
+
+func TestDisplayAPI_GetPrimaryScreen_Ugly(t *testing.T) {
+	svc, c := newTestDisplayAPIService(t)
+	c.RegisterQuery(func(_ *core.Core, q core.Query) core.Result {
+		switch q.(type) {
+		case screen.QueryPrimary:
+			return core.Result{OK: false}
+		default:
+			return core.Result{}
+		}
+	})
+
+	got, err := svc.GetPrimaryScreen()
+
+	require.Error(t, err)
+	assert.Nil(t, got)
+}
+
+func TestDisplayAPI_GetScreenAtPoint_Ugly(t *testing.T) {
+	svc, c := newTestDisplayAPIService(t)
+	c.RegisterQuery(func(_ *core.Core, q core.Query) core.Result {
+		switch q.(type) {
+		case screen.QueryAtPoint:
+			return core.Result{OK: false}
+		default:
+			return core.Result{}
+		}
+	})
+
+	got, err := svc.GetScreenAtPoint(10, 20)
+
+	require.Error(t, err)
+	assert.Nil(t, got)
+}
+
 func TestDisplayAPI_OpenFileDialog_Good(t *testing.T) {
 	svc, c := newTestDisplayAPIService(t)
 	c.Action("dialog.openFile", func(_ context.Context, opts core.Options) core.Result {
@@ -497,6 +548,23 @@ func TestDisplayAPI_ReadClipboardImage_Ugly(t *testing.T) {
 	assert.Nil(t, got)
 }
 
+func TestDisplayAPI_ReadClipboardImage_Ugly_BackendFailure(t *testing.T) {
+	svc, c := newTestDisplayAPIService(t)
+	c.RegisterQuery(func(_ *core.Core, q core.Query) core.Result {
+		switch q.(type) {
+		case clipboard.QueryImage:
+			return core.Result{OK: false}
+		default:
+			return core.Result{}
+		}
+	})
+
+	got, err := svc.ReadClipboardImage()
+
+	require.Error(t, err)
+	assert.Nil(t, got)
+}
+
 func TestDisplayAPI_WriteClipboardImage_Good(t *testing.T) {
 	svc, c := newTestDisplayAPIService(t)
 	var got []byte